[johnsonjo]

> Might have several. It only has one answer if there is only one child, which appears to be the case here.

With context. It does have several which was probably GPs point, and she did not have only one child.

Quick google search turns out that Mary Lee Pfeiffer had 4 children:

Lee Ann DeVette (born 1959) (daughter) Marian Henry (born 1960) (daughter) Tom Cruise (born 1962) (son) Cass Mapother (born 1964) (daughter)

So saying "Who is Mary Lee Pfeiffer's child?" would have 4 possible answers (which is several) with all known context. Whereas like GP was saying "Who is Mary Lee Pfeiffer's son?" would have 1 identifying answer, Tom Cruise with the same context.

> In this case, the correct would always include “Tom Cruise” even if it needed a clarifying “there might be others I have no knowledge of”.

I agree with this by the way.