Answer:
 Y is probably excitatory and Z is probably inhibitory
Explanation:
- Two neurons communicate with each other generally by releasing neurotransmitters.
- The neuron which releases the neurotransmitter is termed as presynaptic neuron and the neuron to which the neurotransmitter binds to exert its effects is called as postsynaptic neuron.
- Based on the nature of the neurotransmitter released, the presynaptic neurons can either be inhibitory or excitatory in nature.
- The change in the membrane potential of the postsynaptic neurons depends on the total sum of inputs coming from different pre synaptic neurons at a given time.
- From the given situation, the stimulation by X alone is causing deploarization of 0.5 mV which shows that it is causing excitation, and since depolarization is increasing when X and Y are stimulaneously stimulated Y is also excitatory in nature. However the depolarisation is not occurring when X and Z are stimualted together and hence, Z is probably inhibitory in nature. 
 
        
             
        
        
        
The changing quantities in an experiment are called variables. A variable refers to any trait, factor, or a condition, which can prevail in distinct amounts or kinds. An experiment generally exhibits three kinds of variables: independent, dependent, and controlled.
The independent variable refers to the one, which is modified. On the other hand, the dependent variable is implied to observe that how it reacts with the change made to the independent variable. The controlled variables refer to the quantities, which one wants to remain constant.
In the given case, that is, heating a cup of water to witness that whether the sugar will get more easily dissolve. In this, the independent variable refers to the temperature of the water determined in degrees Centigrade. The dependent variable refers to the amount of sugar, which dissolves completely measured in grams.
In this, the controlled variables are stirring and type of sugar. As more stirring might elevate the amount of sugar that dissolves, and different kind of sugars might dissolve in distinct concentrations. So, in order to make sure a fair test, there is a need to keep these variables similar for each cup of water.
 
        
             
        
        
        
Hey ur answer should be A intelligence 
 
        
             
        
        
        
1. Scientific method is the techniques that scientists used to carry out investigation process. It is made up of five steps, which are:
a. Observation: this is the stage in which a scientist make an observation to which he did not have an explanation.
b. Formation of a research question:  in accordance to observation made, the scientist form a question on which his experiment will be based
c. Formation of hypothesis: at this stage the scientist offers a proposed explanation for the observation which he had made and state what he expects at the end of the experiment.
d. Conduction of the experiment: at this stage the scientist carry out the experiment using appropriate means.
e. Analysis of data and drawing of conclusion: this is last stage of the investigation, at this stage, the scientist analysis the results he obtained and draw a conclusion based on the results of the data.
2. Scientists used scientific method to carry out scientific investigations because the method minimize the influence of bias and prejudice in the experiments that they carry out. The method provides an objective, standardized approach to scientific investigation; this result in reproducible results which can be achieved by other scientists in every parts of the world. The method also helps to minimize errors during investigation.
        
             
        
        
        
Answer:
Crossing over
Explanation:
Crossing over is the process during which two chromatids of two homologous chromosomes exchange part of their genetic segments. It occurs during the pachytene stage of prophase I of meiosis I. 
Linked genes are mostly inherited together and do not exhibit independent assortment. However, when linked genes are present far apart from each other on the same chromosome, crossing over can occur between them to produce recombinant chromatids. Therefore, crossing over can break the linkage and produce recombinant progeny as it occurs during the independent assortment of unlinked genes.