She _____ your birthday party, but she had to look after her mother in hospital.
The fog was so heavy this morning that drivers could hardly ______ thethings just ten meters away from them.
I ______ a flu when I was on a spring outing with my classmates.
The weather that day may not be as good as expected, in ________ case we will have to put off the event.
Chemical pollution will bring about a threat to agriculture and food chain, and ________ to human health.
—Jenny, I hate to say it, but you really must go! —________.