It certainly isn't the last one. A theory is close to a guess. It fits all the known facts, but there is usually something missing. If someone figures out what is missing, usually by experiment, then the theory become a fact.
The rest of them (1 2 an 3) can all be true. 3 is the least viable. You have to be able to come up with a counter example to reject a theory.
I'm not sure about 2. New phenomena can still be part of current theories. Reluctantly, I wouldn't choose 2 because
1 is the best answer of a very poor lot. Do not be surprised if you use it, that it turns out to be wrong.
A frame-shift mutation would occur. This is because a
deletion will cause a change in codon sequence from the point of mutation to
the end of the mRNA. If the mutation is
closer to the start of the mRNA, the larger the effect of the mutation on the
translated protein.
The corpus callosum does allow the hemispheres of the brain to have an access to the information in both sides therefore the information need to cross the corpus callosum yet if it would not cross into the corpus callosum the person would respond the opposite way as then.
