instruction:
In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
question:
Ozone is a form of oxygen in which the molecule contains _ atoms instead of two.
answer:
three


question:
Optical isomers differ in the arrangement of _ groups around a chiral carbon.
answer:
four


question:
Natural tungsten contains _ stable isotopes.
answer:

five