Answer:
The correct answer is (a)
Step-by-step explanation:
Even all answers might be correct, the only way to prevent 100% the spread of AIDS is using condoms.
Avoiding high risk behaviors depends on what you may consider a high risk behaviour, and different persons may have different opinions regarding this.
Even if you know your partner`s sexual history, it is impòssible to know 100% sure if those were safe interactions or not.
When you use condoms, your partner could be HV/AIDS carrier, and you will not be infected.
I hope it helps!