Each member of a class sampled a piece of PTC testing paper. Thirty people sampled the chemical. Twenty persons were tasters. How many had homozygous recessive genes?
30
10-30
20
10

The first signs of cellular differentiation occur in the blastocyst. why is cellular differentiation important for the development of a fully formed human infant?

Which statement best describes how the loudness of the sound affects the high-pressure region created by the sound wave? a. a louder sound has no effect on the pressure created. b. a louder sound means a high-pressure region that is higher. c. a louder sound means a high-pressure region that is not as high.

Which chemical reaction shows photosynthesis? a. water + carbon dioxide + sunlight → oxygen + glucose b. carbon + oxygen → carbon dioxide c. hydrogen + oxygen → water d. nitrogen + hydrogen → ammonia