If it isn’t him, who________ it be

I don’t know why he has made such a silly mistake in the exam. —— He ____________ it before he handed in the paper.

It is usually warm here in March, but it _____ be rather cold sometimes.[ ]

carrots，potatoes, onions and any other vegetables_____and immediately use or throw away any which show signs of rotting.

Hello, Mary. This isJoe. —_____________.—Nice to meet you, too.