what is a direct object and a subject compliment?

Answer 1

http://www.ucalgary.ca/UofC/eduweb/grammar/index.htm
Click on Sentence Elements on the left and then on the links you need.

http://grammar.ccc.commnet.edu/grammar/index2.htm
You can also look them up here, alphabetically.

Answer 2

Direct objects are nouns or pronouns that receive the action of the verb. They follow action verbs.

Examples:

Shirley hit him.
I like chocolate.
Logan is practicing the guitar.

Subject complements are nouns or adjectives that mean the same as or describe the subject. They follow linking verbs.

Our teacher is brilliant.
Mr. Jones was sick.
Steve and Joe are great football players.

Check this site for more information.

http://www.uottawa.ca/academic/arts/writcent/hypergrammar/objcompl.html