Respuesta :
The corrrect option is D.
Since the scientist was trying to determine if substance A affect the rate of reaction of X and Y, the best thing to do is to make substance X and Y to react together first, he should then measure the time taken for the reaction to take place. Next, he should make X and Y to react together again, but this time in the presence of A. The time taken for the reaction to occur should be measures. The scientist can now compared the two time measurements and decide if there are difference between them or not.
Since the scientist was trying to determine if substance A affect the rate of reaction of X and Y, the best thing to do is to make substance X and Y to react together first, he should then measure the time taken for the reaction to take place. Next, he should make X and Y to react together again, but this time in the presence of A. The time taken for the reaction to occur should be measures. The scientist can now compared the two time measurements and decide if there are difference between them or not.
The answer would be First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is an enzyme.