He studies so hard to avoid （ ） at the bottom of the class.

She is very （ ） to his ugly appearance.

The kidney transplant operation was _____ complicated， so the operating team had to take special care to ensure its success.

I cannot tell the_____difference between the twins.

You needn’t introduce him to me. I’ve met him on several _____.

It was not known （ ） he had said during the interview.

（ ） when she started complaining.

The defense computers calculate way to （ ） the enemy missiles.

She （ ） tell white lies to make people feel better, to smooth things over.

I recognized John （ ） he entered the room.

Such problems （ ） air pollution and traffic jams are becoming more and more serious in some big cities.

The twin sisters look so much alike that I could never tell _____.