A logical inference is not a guess.
You deduced this with what 'someone said'. The actual list of options doesn't say that -
"Obvious" option?
Again, an abstinence and contraception option is not relevant to determining weather or not abstinence only sex ed is effective.
Besides, traditional sex ed has already been proven a failure.
So, if traditional sex ed is a 'proven' failure why include it? The obvious one to include against abstinence only sex is a combination of both. I still don't see that option when I read that list... I would rather not go on 'inference'.
And once again - you are trusting teens to tell the truth about sex. What was your 'proof' that traditional sex ed wasn't successful in whatever place you found where it was proven a failure? Was that study also dependent on teens to tell the truth - or do you have 'harder' evidence. STDs or pregnancy rates for instance?