Why do psychologists perfrom twin studies in orer to determine the influence of genetics on intelligence?

Psychologists perform twin studies in order to determine the extent to which genetics influence intelligence levels. Since identical twins share 100% of their genetics, it follows that their intelligence levels should be quite similar given that intelligence is genetically determined. However, when identical twins are found to have varying intelligence levels, it indicates that external factors (or nurture) play a role in intelligence. Therefore, psychologists perform twin studies in order to determine the extent to which genetics and non-genetic factors determine intelligence levels. 

Idont know which one is right   but i know that c is wrong and a might be wrong

Hamlet's fourth soliloquy is probably his most famous one - "to be or not to be."it is rather different from his previous soliloquies because now he is contemplating something that didn't come up before - suicide. he is thinking whether it is worth it to fight to find his father's murderer when in the end all of them are going to die, so why not die sooner than later. he is contemplating if he should go on fighting or just kill himself and end it all, which is why this soliloquy in particular is rather depressing, hesitant, and gives a deeper insight into hamlet's madness.