I found this in an exam paper:
A German mother and teacher has written to the newspaper about libraries.
Shouldn't it be "A German mother and teacher have written to the newspaper about libraries." since there are multiple people? "Has" does not sound right to me.
Best Answer
If it's referring to one person who is both a mother and teacher (which, at a glance, is what is inferred) then "has" is correct. If it's two separate people who have written in then "have" would be correct instead.
explained here: http://writingexplained.org/has-vs-have-difference
The verb "have" is conjugated as "has" when it's one person ("he/she has joined the gym"), whereas when there are multiple people it's "have" ("They have joined the gym").