It is______ a sharp knife ______I can use it to cut open a hard pumpkin.[ ]

On March 23, many people took part in “_________ Lights” activity to help save energy.

The park ______we visited yesterday is an excellent one .

According to the recent research, heavy coffee drinking and heart attack is not necessarily ______ and effect.

How pleasant is to go fishing with my father! — Yes. Parents and children should spend more time together.