In an investigation to determine a factor that affects the growth of rats, a student exposed 100 rats of the same age and species to identical conditions, except for the amount of living space and the amount of food each rat received. Each day the student measured and recorded the weight of each rat. State one major error that the student made in performing this

Violating 'Ceteris Paribus' {Other factors constant} assumption, as both food & space are varied (simultaneously)

Explanation:

Weight Growth is the dependent (effected) variable in this case. And, independent (causal) variables are food amount are living space respectively.

However particular independent factor's (food or living space) impact on dependent variable ie weight growth : can be determined only by - examining individual variable (food or living space) impact on weight growth. So, either of the two variables should be varied, & not both should be varied simultaneously.

This would imply depiction of each factor's clearer individual impact on the dependent factor.

answer; i believe the correct answer is ( proteins );