Xu Xu, a husband-to-be, has an ambiguous message.

According to the meaning of the question, the following table is obtained:

As can be seen from the table, Xiao Liu is not a farmer and Xiao Zhang is not a farmer, so Xiao Xu is a farmer. Xiao Xu is older than that soldier and that farmer is younger than Xiao Zhang.

So Xiao Zhang is neither a soldier nor a farmer, so Xiao Zhang is a worker.

Therefore, choose: B.