"Please wait for a moment."
I think this question is too easy! There are only two options for the answer. Firstly "请等一下", which is correct. Secondly, "等". Given that the audio is easily identifiable as 4 syllables, one can easily guess that "等" cannot be correct in itself. Perhaps some more "wrong" options would make it more of a challenging question. Alternatively, break up the "correct" answer into its constituent characters.