The two proteins directly involved in muscle contraction are broadly called . During an exercise where muscles do not shorten, contractions have occurred. a. has an affinity for myosin binding sites in the absence of calcium. b. is a missing protein in Duschenne's muscular dystrophy. c. The cell membrane of a muscle fiber is the .

the answer will be a) proteins i believe

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

i hope this : )

and after water is usually warmed by the sun the water temperature raises and then evaporates .