Please select the correct answer:

The first five questions use alphabet ? = {a, b} and have exactly one correct answer. Recall that superscript plus means "one or more" and that zero counts as an even number. For this and the next two questions, say which prose description goes with the regular expression at top. The first char in a string has index 1, not 0. Regular expression: (ab*a)+ Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Nonempty strings with an even number of a's. Strings with a positive even number of a's. Strings that have an even number of a's and that begin and end with a --- and with even blocks of a's left over when you take the beginning and ending a's away (or with left over if the string is aa). d Strings that have an even number of a's and never have more than two a's in a row. e Strings with a positive even number of a's and an odd number of b's