.It was ______ the 19th century_____ heat was considered to be a form of energy.
Not once________to Michael that he could one day become a top student in his class.
Not until he went through real hardship ________ the love we have for our families is important.
—Do you hear Jim and Mary broke up?—No,I haven't heard of it,and neither ________ about it.
The teacher together with the students ________ discussing Reading Skills that ________ newly published in America.
So much progress ________ made in studies that he is sure to pass the coming examination.