Provide English description for the regular expressions listed below.
ab.cd
ab*cd
ab.*cd
abb*cd
^abc
^abc$
[abc]d
[^abc]d
[A-Z]xy
[A-Z_][a-zA-Z0-9]*
(For instance, the regular expression "x*tiny_mce_markerquot; could be described as "zero or more x at the end of a line".)