A chemist is conducting an experiment to find an enzyme that speeds up a reaction between Chemical A and Chemical B. The chemist places Chemical A and Chemical B together in a beaker and then times how long it takes for the reaction to occur Next,
the chemist places the same amount of the two chemicals in a second identical beaker. The chemist adds an enzyme and then
times how long the reaction takes to occur
Did the chemist use adequate experimental controls?

The correct option is;

C. Yes, the first chemical reaction (without the enzyme) acted as a control

Explanation:

A scientific control is a parallel observation or an experiment that serves as a measure to better improve the experimental result reliability, by comparing the outcome of the control experiment or observation with the outcome of the other observations or measurements to which has been applied an experimental treatment.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.