Which of the following is true of dna? a. there are six nitrogenous bases involved. b. cytosine can pair with guanine and adenine. c. there are four nitrogenous bases involved. d. adenine always pairs with guanine.

Some birds look for food near cattle and other livestock. the movement of the cattle churns up the ground, making insects available to the birds. the cattle appear to be unaffected by the presence of the birds. what kind of relationship exists between the birds and the cattle? o a. parasitism o b. commensalism o c. predation o d. mutualism

Which worm has eyespots that are used to detect light? a fluke b marine worm c planarian d tapeworm

Which of the following is a limitation of a clinical trial? a.)amount of random assignments b.)hospital cost c.)number of test tubes d.)amount of peer review