instruction:
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.
question:
Girls have ____ ovaries.
answer:
two


question:
Avian kidneys have ____ kinds of nephrons.
answer:
two


question:
Humanity is responsible for five or ____ billion tons a year.
answer:

six