_____ a certain doubt among the workers as to whether he could finish the task in a short time.
I ____ to visit you later that day, but I had to phone and cancel.
Animals are obviously _____ lower form of life than ______ man.
Recycling is one way to protect the environment; reusing is _____.
I would have gone to my cousin’s birthday party last night, but I ______ available.
______ is often the case in science, there is no simple answer