<span>B is the correct answer. The beginning of DNA replication occurs with the unwinding of the DNA helix by a special enzyme. The two strands that form the helix then create a replication fork. The two strands are then oriented differently, one becoming the 'leading strand' and one the 'lagging strand'. </span>
The answer would be C, double fertilization produces a triploid zygote and a tripped endosperm!
Parietal cells produce gastric acid (hydrochloric acid) in response to histamine (via H2 receptors), acetylcholine (M3 receptors) and gastrin (gastrin receptors). Parietal cells contain an extensive secretory network (called canaliculi) from which the HCl is secreted by active transport into the stomach.
Not true, certain chemical transmitters stimulate certain receptors
