Lipid A

A. A compound that removes H+ ions from a solution: This describes a base, since bases decrease hydrogen ion concentration by binding or neutralizing H+ ions, which is the opposite of what acids do.

B. A compound that releases OH- ions into a solution: This also characterizes a base, such as sodium hydroxide, which increases hydroxide ion concentration rather than contributing hydrogen ions.

C. A compound that releases H+ ions into a solution: Acids are substances that increase the hydrogen ion concentration in a solution by releasing H+ ions, making the solution more acidic and lowering its pH.

A. growing corn plants with various amounts of fertilizer: Using corn plants introduces a different species, which makes results irrelevant to the effect of fertilizer on tomato plants.

B. growing tomato plants with various amounts of fertilizer: This is part of the experimental group rather than a control, as it tests different fertilizer levels rather than providing a baseline for comparison.

C. growing corn plants without fertilizer: Corn plants are not suitable because the research question focuses on tomato plants. A valid control must match the species being studied.

D. growing tomato plants without fertilizer: This is the correct control, as it provides a baseline growth rate for tomato plants without fertilizer, allowing meaningful comparison with fertilized groups.