Three unbiased coins are tossed. What is the probability of getting at most two heads?

Answer: Option D

Getting at most Two heads means 0 to 2 but not more than 2
Here S = {TTT, TTH, THT, HTT, THH, HTH, HHT, HHH}
Let E = event of getting at most two heads
Then E = {TTT, TTH, THT, HTT, THH, HTH, HHT}
$$\therefore P\left(E\right)=\frac{n\left(E\right)}{n\left(S\right)}=\frac{7}{8}$$