[Grammar] Question tags

[lille82]

Someone must have seen the mugger, mustn't they? Why can't we use "mustn't s/he"?

Thanks in advance.

 

[5jj]

Someone must have seen the mugger, mustn't they? Why can't we use "mustn't s/he"

We can.

 

[lille82]

This test book is so strict... It accepts only one good solution.

 

[5jj]

This test book is so strict... It accepts only one good solution.

Then throw it away.

 

[lille82]

I was thinking of that... and get a nice one instead that allows at least two good solutions.