A student placed some clean rocks in a clear plastic jar. The jar was filled with clean water and covered with a lid. The student then shook the jar up for five minutes. The student noted that smaller pieces had broken off some of the rocks and that there was a fine grit on the bottom of the jar. Which change of Earth's surface was the student modeling? * A. mechanical weathering
B. chemical weathering
C. erosion of sediments
D. forming deltas
E. I don't know

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.

Which statement describes the punctuated equilibrium theory?

Kara has a plant that produces either purple or white flowers. she crosses a plant that has two recessive alleles for white flowers with a plant that has two dominant alleles for purple flowers. which result would be true of all of the offspring? a) all of the offspring would have two recessive alleles and white flowers. b) all of the offspring would have two dominant alleles and purple flowers. c) all of the offspring would have one recessive allele, one dominant allele, and white flowers. d) all of the offspring would have one recessive allele, one dominant allele, and purple flowers