I made a suggestion ________ he ________ to Australia for further education.
It is uncertain ________ side effect the medicine will bring about, although about two thousand patients have taken it.(2010·浙江)
Part of the reason Charles Dickens loved his own novel, David Copperfield, was ________ it was rather closely modeled on his own life.(2010·北京)
He didn't go by bike with me.That's ________ there was something wrong with his bike.
They________have arrived at lunchtime but their flight was delayed.(2011·全国 )
—Must I turn off the gas after cooking?—Of course.You can never be ________careful with that.