instruction:
In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
question:
Gravity is the weakest of all _ forces but unlike the others it has an unlimited range.
answer:
four


question:
Oceanographers now understand the oceanic circulation much better than _ years ago.
answer:
ten


question:
Man therefore has _ different substances interacting with each other.
answer:

two


