单项选择题

Which of the underline expressions is the hedging of the following sentences.There is no difficulty in explaining how a structure such as an eye or a feather contributes to survival and reproduction; the difficulty is in thinking of a series of steps by which it could have arisen.
A、There is no difficulty in explaining how a structure such as an eye or a feather contributes to survival and reproduction; the difficulty is in thinking of a series of steps by which it could have arisen.
B、There is no difficulty in explaining how a structure such as an eye or a feather contributes to survival and reproduction; the difficulty is in thinking of a series of steps by which it could have arisen.
C、There is no difficulty in explaining how a structure such as an eye or a feather contributes to survival and reproduction; the difficulty is in thinking of a series of steps by which it could have arisen.
D、There is no difficulty in explaining how a structure such as an eye or a feather contributes to survival and reproduction; the difficulty is in thinking of a series of steps by which it could have arisen.