请问计算器怎么按？

问题如下：

On a multiple-choice exam with four choices for each of six questions, what is the probability that a student gets fewer than two questions correct simply by guessing?

选项：

A.

0.46%

B.

23.73%

C.

35.60%

D.

53.39%

解释：

We use the density given by Equation: $f{(x)}={(\begin{array}{l}n\\x\end{array})}p^x{(1-p)}^{n-x}$. The number of trials is n = 6. The probability of guessing correctly just by chance is p = 1/4 = 0.25. The probability of zero lucky guesses is $C_6^00.25^00.75^6=0.75^6=0.17798$. The probability of one lucky guess is $C_6^10.25^10.75^5=6\times0.25\times0.75^5=0.35596$. The sum is 0.5339.

Note that the same analysis can be applied to the distribution of scores on an FRM examination with 100 questions. It would be virtually impossible to have a score of zero, assuming random guesses; this probability is $0.75^{100}=3.2E-13$. Also, the expected percentage score under random guesses is p = 25%.