(A) will begin at 9 a.m. and continue until the supply lasts
(B) begins at 9 a.m., continuing until the supply lasts
(C) will begin at 9 a.m. and, until the supply lasts, will continue
(D) begins at 9 a.m. and, as long as the supply may last, it continues
(E) will begin at 9 a.m. and continue as long as the supply lasts
Until is used to express a point of time in the future, for example: We danced until dawn.
As long as means that one thing will occur while another thing is still true (conditional).
Example: I'll stay as long as you need me.
A, B, and C are incorrect because of the use of until.
D is wordy and awkward.
E is the best choice. as long as is appropriate here.
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