In an experimental investigation, the variable that the researcher changes or manipulates in order to see its effects is called the variable

Independent variable.

Explanation:

In the investigation there are two type of variables

1. Independent variables

2. Dependent variables

Independent variables are the variables which is independent and cam changes without affecting any other variables.But on the other hand dependent variables are the variable which depends on the independent variable.

 y=f(x)

Here y is the dependent variable and x is the independent variable.

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation: