24. The task was difficult, but Helen’s _____expression let me know that she would not give up.
A survey of the opinions of experts___that three hours of outdoor exercise a week___good for one’s health.
When asked why he went there,he said he was sent there___for a space flight.
Scientists are convinced___the positive effect of laughter___physical and mental health.()
Don’t take too much of the medicine;it does you more harm than good if you______.
—Will you join us in the game? —Thank you,_______