Lets consider the binary strings in lexicographic order for lengths starting from $0$ on wards, which will be $\{\epsilon, 0, 1, 01, 10, 11, 000, 001, 010, \ldots \}.$
Here, $p = \Sigma^*$ and generates every binary string.
$\epsilon, 0, 1, 01, 10,11, 000, 001$ are generated by $q$ also but $010$ is not generated by $q.$ $\mid 010 \mid = 3.$
Correct answer: $3.$