Alternations, denoted by the | character, match a single item out of several possible items separated by the vertical bar. When used inside a character class, it will match characters; when used inside a group, it will match entire expressions (i.e., everything to the left or everything to the right of the vertical bar). We must use parentheses to limit the use of alternations.

For example:

• (Bob|Kevin|Stuart) will match either Bob or Kevin or Stuart.
• ([a-f]|[A-F]) will match any of the following characters: a, b, c, d, e, f, A, B, C, D, E, or F.

Task

Given a test string, , write a RegEx that matches under the following conditions:

• must start with Mr., Mrs., Ms., Dr. or Er..
• The rest of the string must contain only one or more English alphabetic letters (upper and lowercase).

Note: This is a RegEx-only challenge. You are not required to write code; you simply need to fill in the blank.