Assume that the following files are in the working directory: $ ls
intro notesb ref2 section1 section3 section4b
notesa ref1 ref3 section2 section4a sentrev

Give commands for each of the following, using wildcards to express filenames with as few characters as possible.
a. List all files that begin with section.
b. List the section1, section2, and section3 files only.
c. List the intro file only.
d. List the section1, section3, ref1, and ref3 files.