Which type of experiment involves changing only one variable at a time

Based on the data in your tables, did the light-colored moths have a higher or lower survival rate after the industrial revolution?

Round seeds and yellow seed color are dominant to wrinkled seeds and green seed color. which punnett square represents the correct way to set up the cross rryy  ´  rryy? 

What kinds of molecules can pass through the cell membrane without any problem?