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.
The purpose of meiosis is to shuffle genetic information and cut the cellular chromosome number in half, from 46 chromosomes to 23 chromosomes. ... In humans, the reduction division results in two sperm cells each with 23 chromosomes or an egg cell with 23 chromosomes and one discarded polar body.
2
The mass of an object won't actually be the reason whether something will sink or float, because 2 tonne boats can float.
Many factors like density, Archimedes' principle, go in to determining whether something will sink or float
