Answer:
Constant variables
Explanation:
Elaina's investigation lacked the critical ingredient of constant variables which are important components of every scientific investigation. In every research, there are 3 important variables, namely:
1. Dependent variables: the actual variable to be measured during the course of investigations and whose values are dependent on another variable (independent variable) supplied by the investigators.
2. Independent variable: one of the variables that are supplied by investigators whose values are often manipulated to see the kind of changes it will cause to the dependent variable. 
3. Constant variables: other variables that are neither independent nor dependent but constant for all the various experimental groups in investigations. 
 
        
             
        
        
        
Answer:
The nervous system releases neurotransmitters at synapses at specific target cells & The endocrine system reacts more slowly to stimuli, often taking seconds to days. 
Explanation:
The nervous system is very specific with where the neurotransmitters go so they will affect target cells. The endocrine system is slower than the nervous system because the hormones travel through the blood so it takes much longer to reach the designated area. 
 
        
             
        
        
        
Answer:The white blood cells involved in innate immunity are. Monocytes (which develop into macrophages). Neutrophils. Eosinophils. Basophils. Natural killer cells.
Explanation: MERK MELLS
 
        
             
        
        
        
Answer:
False
Explanation:
condensation points is the complete opposite of boiling points. Condensation point is when its is so cold that water goes from a gas to a liquid and boiling points is when water goes from liquid to gas because it is so hot. Hope this help! -3-
 
        
             
        
        
        
Air that resists vertical movement is said to be stable. The vertical movement of air is referred to as convection, while advection involves the horizontal movement of air and heat energy transference, Temperature differences at the Erath's surface occur wherever there are differences in surfaces substances.