Nanette Must Pass Through Three Doors as She Walks from Her

Multiple Choice

Nanette must pass through three doors as she walks from her company's foyer to her office. Each of these doors may be locked or unlocked.
Let B be the event that exactly two doors are locked. List the outcomes of B
Designate "locked" and U" designate "unlocked".]

A) {LLU, LUL, ULL}
B) {LLU, LUL, ULL, LUU, ULU, UUL}
C) {LLL, LLU, LUL, LUU, ULL, ULU, UUL, UUU}
D) None of these.