One Reason Employers Are the Predominant Source of Health Insurance

One reason employers are the predominant source of health insurance is because:

A) insuring at the firm level reduces the extent to which insurance has moral hazard effects.
B) insuring at the firm level allows insurers to create large insurance pools with a predictable distribution of medical risk.
C) government regulation requires that employee compensation include a non-cash component and health insurance premiums qualify.
D) it is efficient from society's perspective to link employment and health insurance coverage.