If he takes on this work, he will have no choice but ___ an even greater challenge.
A meets B meeting C meet D to meet
I can see that most native speakers say no choice but to do, but there are still some dropping the to saying no choice but do.
Do both C and D work?
Kindly share your points with me.
Thank you very much.

D is the standard choice.
C does not sound good to me.

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Hi, Clive. Thank you so much for so many times helping me.
" No choice but to " is pretty much a fixed expression.