5) why can the cutting down of trees be damaging to the environment?
a) trees bring about global warming.
b) trees absorb carbon dioxide and give out oxygen.
c) cutting trees has no effect on the environment.
d) trees bring shade and protect humans from sunburn.

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.