user
What force and strangth cannot get through,            I with a gentle touch can do,        and many in the street would stand,           were I not a friend at hand. 
A: first floor
B: dust
C: stand
D: key that opens lock
E: smooth
assistant
<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

<|end_of_thought|>

<|begin_of_solution|>

D

<|end_of_solution|>