Statement 1: All polymers are compounds.
Statement 2: Some compounds are not plastics.
Statement 3: All plastics are synthetic.

Which of the following must be false?

Given,

All polymers are compounds.

Some compounds are not plastics.

All plastics are synthetic.

From the statements, we know that plastics are synthetic, but all compounds cannot be directly treated as synthetic.

Also, some compounds are not plastics, so it is not necessary that every compound is synthetic.

Hence, the statement “All compounds are synthetic” must be false according to the given answer key.