The term ______ refers to the ability of a microbe to exist in a wide range of conditions.

A. Are acellular: Subunit vaccines contain only parts of the pathogen, not the whole cell or organism, which reduces the risk of adverse reactions.

B. Are administered in food: Vaccines are generally not delivered through food; this does not contribute to their safety.

C. Do not pose a risk for causing the disease: Because they contain only specific antigens and no live pathogen, subunit vaccines cannot revert to a virulent form or cause infection.

D. Are acellular and do not pose a risk for causing the disease: Subunit vaccines are acellular and composed of purified antigens, making them both safer and incapable of causing disease.

A. Proteins are permanently denatured: Heat can denature proteins by disrupting noncovalent interactions; however, saying “permanently” is too absolute — some proteins may refold if conditions return to normal.
B. Membranes become too fluid for proper function: Elevated temperatures increase membrane fluidity (phospholipid tails become more disordered), impairing membrane integrity and function. This is true but incomplete alone.
C. Hydrogen bonds within molecules are broken: High temperature disrupts hydrogen bonds (and other weak interactions) that stabilize protein secondary/tertiary structure and nucleic acids; again this is true but incomplete by itself.
D. Hydrogen bonds are broken and proteins are permanently denatured: This combines two effects (bond disruption and denaturation). It’s closer, but “permanently” may be incorrect in some cases where refolding is possible — and it still omits membrane effects.
E. Hydrogen bonds are broken, proteins are denatured, and membranes become too fluid: High temperatures disrupt hydrogen bonding, cause protein denaturation, and increase membrane fluidity, all of which together explain why growth stops above the maximum growth temperature.