Regular expression question in Linux (Only write the regular expression. Do not include the egrep command and do not enclose it in single or double quotes.):

1. Write a regular expression that you could use with egrep that will match all sentences that contain exactly four words separated by a space with a punctuation mark at the end. Assume that the first word of a sentence is capitalized. (Some lines may contain more than one sentence.) Use the :alpha:, :upper: and :punct: classes where appropriate.

2. Write a regular expression that you could use with egrep that will match all lines in which the letters (upper or lower case) a, b, c, and d appear in that order (not necessarily consecutively). This should, for instance, find a bat can die.

3. Write a regular expression that you could use with egrep that will match lines in the names.txt file that have cities whose names are multiple (i.e. 2 or more) words.