I'm having trouble with transitive and intransitive verbs. I have to pick out the verb and tell if it's transitive or intransitive.

Some reach a height of 120 feet.

reach=intransitive

The stems measure a foot in diameter.

measure=intransitive

You have transitive and intransitive turned around.

The root word trans- comes from the Latin meaning "across." A transitive verb carries the action across -- from the subject to the direct object. An intransitive verb does not carry any action across; there is no direct object.

If a word answers "what" after the verb, it is probably a transitive verb.

reach -- WHAT? (height)
measure -- WHAT? (foot)