Answer:
This question is asking to identify the variable in the experimental statement.
The eye chart is the CONTROL VARIABLE
Explanation:
An experiment consists of several variables to look out for in order to achieve any significant result. These variables are independent variables, dependent variables and control variables. Although independent and dependent variables are the major experimental variables, but control variables are also important.
A control variable is the variable that remains constant or unchanged throughout the experiment. Any change to the control variable will affect the dependent and independent variables. In this question, the eye chart is the CONTROL VARIABLE because it remains constant or unchanged. The same eye chart is used for the experiment.
N.B: The distance to the eye chart is the independent variable while the number of letters visible on the line is the dependent variable. Hence, changing the eye chart (control variable) will affect the distance and the number of letters visible.
The physical expression of genes are phenotype. Phenotype is the expression of the gene by the appearnace of the organism. It is the characteristics of that trait.
Examples : When pigment is made in our eyes, height ( tall and short) , weight, blond hair is the phenotype for the blond hair genotype and skin colour( black, white ) is the phenotype trait.
The nervous system<span> is like a highway along which </span>your <span>brain sends and receives information about what is happening in the body and around it. This highway is made up of billions of nerve cells, or neurons (say new-rons) which join together to make </span>nerves<span>. A nerve is a fibre that sends impulses through the body.</span>
