In a controlled experiment, a scientist is studying how long it takes pea plants growing in different soil types to develop flower buds. What is the manipulated independent variable?

a) type of soil used
b) number of flower buds produced
c) how long it takes for flower buds to develop
d) the type of pea plant being grown

A, C is dependent variable

In a controlled experiment, the manipulated independent variable is the variable that the scientist intentionally changes or controls to see its effect on the outcome of the experiment. In this case, the scientist is studying how long it takes pea plants growing in different soil types to develop flower buds.

To determine the manipulated independent variable, we need to identify the variable that is intentionally changed by the scientist. In this experiment, the scientist is specifically studying the effect of soil types on the time it takes for flower buds to develop.

Therefore, the manipulated independent variable in this experiment is a) the type of soil used.