Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Q: International trade is a ____ way street.

A: two
****
Q: Female smokers enter menopause an average of ____ years earlier than nonsmokers.

A: five
****
Q: All vertebrates produce interferons, and all appear to produce the ____ major classes.

A:
three
****