Which statement is true of crossing over
a- what occurs during prophase of mitosis
b- it allows for genetic variation
c-it occurs only in animals

Which statement about the immune system is false? a. lymphocytes reduce inflammation, b. b cells remember specific pathogens. c. most white blood cells kill bacteria d. white blood cells are made in lymph nodes.

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.

The more rapidly sedimentation occurs, the more likely it is that the remains will successfully form a fossil. as sedimentation continues, what happens to the amount of weight settling onto the organism? stays the same increases decreases cuts in half