He must be helping the old man to water the flowers, _____?[ ]

Could it be in the restaurant in ________ you had dinner with meyesterday ________ you left behind your keys and wallet

Frank put the medicine in a top drawer to make sure it would not be _____ to the kids. [ ]

John, have you gone over your lessons learnt this morning—Not yet.—You should know _____.

It is difficult for you to ______ what will happen in space without gravity.