What is the last two digits of 2^20?

The correct answer is option (4) : 76

$2^{10}=1024≡24(mod\, 100)$

$(2^{10})^2≡(24)^2(mod\, 100)$

$2^{20}= 576(mod\, 100)$

$2^{20}= 76 (mod\, 100)$

Hence, the last 2 digits of $2^{20} $ are 76.