What are two processes that must occur to form soil?
a. weathering breaks rocks into minerals and plants die and decay.
b. erosion and weathering
c. plants produce loam and plants produce humus
d. erosion transports mineral particles and plants die and decay

Which of the following is an advantage of using embryonic stem cells in medical research? a. the use of embryonic stem cells is much less expensive than the use of adult stem cells. o b. no living tissue is damaged when scientists use embryonic stem cells. o c. embryonic stem cells are able to differentiate into a wider range of cells than adult stem cells. d. there is no controversy surrounding the use of embryonic stem cells.