Question

my uncle and guardian ---------------invited me to dinner (has/have)

Answer 1

Answer:

my uncle and guardian ---------------invited me to dinner (has/have)

answer: have

explanation: when there is more than one person there will be "have" except I and you.

Answer 2

Answer:

My uncle and guardian has invited me to dinner.

Explanation:

This is a classic case of 'subject-verb-agreement.' When we say 'My uncle and my guardian,' we can use 'have' as we have clearly differentiated two people. In the case given above, we have not specified that the uncle is any different from the guardian.

So we have to assume they are the same person and use 'has.'

I highly recommend 'Wren and Martin' for tough grammar topics like this one.