What is the measure of an angle that is complementary to right angle 42°

In which environment would primary succession occur? a forest with a few remaining trees after a recent wildfire an area of exposed rock after a glacier melts away beach that is exposed to the air at low tide an abandoned baseball field in a small town

Salt in oceans comes from and of rocks

When did stem cell research become known ? who discovered stem cell? what experiments or studies have been conducted so far?