why was it critical for good pioneer trails going west to have a decent route through the Rocky mountains

How should the student cite this source using mla citation format?

Which statement best describes the response by the united states and its allies to the berlin blockade? planes dropped tons of supplies around the city each day. trucks smuggled tons of supplies into berlin about once a week. tons of supplies were delivered to west berlin by boats. tons of supplies were purchased from east berlin each day.

What were four reasons for the decline of spain as a world power