Experiments of this kind ________ in both the U. S. and Europe well before the Second World War.[ ]

I think you can join an English club toimprove your English.—___________.

Linda ________ half of the report already. And she will finish the rest this afternoon.

On the double 11th day, my uncle’s online store has successfully sold _____ shoes as last year, that is, it can hardly make ______ progress.

Mum, I’m tired.—Why not ________