[tex] 5 \times 10 = 50 [/tex], so option C is surely wrong.
Moreover, [tex] 2 \times \frac{1}{100} = 0.02 [/tex]
So, if you add the two, you have
[tex] 50+0.02 = 50.02 [/tex]
which is option E. But if you add a zero after the decimal expansion of a number, the number doesn't change:
[tex] 50.02=50.020 [/tex]
So option A is fine as well
