We are often told ________ at people in trouble．

A．not to smile

B．to smile

C．not to laugh

D．to laugh

The flowers ________ every day．Or they’ll die．

A．must water

B．can be watered

C．should water

D．must be watered

I know she won't come to join us unless she ________ to．

A．tells

B．has told

C．is told