To find the probability of picking a consonant from the sample space \( S = {a, b, c, d, e, f} \), we first identify the consonants and the total number of letters in the sample space.
In this case, the vowels are \( {a, e} \), and the consonants are \( {b, c, d, f} \).
There are 4 consonants (b, c, d, f) and a total of 6 letters in the sample space.
The probability of picking a consonant is given by the formula:
\[ \text{Probability of consonant} = \frac{\text{Number of consonants}}{\text{Total number of letters}} = \frac{4}{6} \]
Now, we can simplify \( \frac{4}{6} \):
\[ \frac{4}{6} = \frac{2}{3} \]
Thus, the probability of picking a consonant is \( \frac{2}{3} \).
The correct answer is \( \frac{2}{3} \).