Everybody knows that condoms can avoid pregnancy.
Why is the IELTS examiner confused by this? Because it creates in the mind of the examiner a kind of impossible cartoon image showing two condoms having sex in such a way that the female condom will not become pregnant.
Indonesians need to consider the difference between avoid (menghindar) and prevent (mencegah):
Think of the condom as the agent that does the preventing. Humans can avoid pregnancy through the use of condoms, where the condom is the agent of prevention. So..