An independent clause is one that could stand alone as a
complete sentence.
Example:
The
crew could see the whale, which had surfaced only 50m behind them.
independent
clause
subordinate clause
(i.e., could stand
alone) (i.e.,
could not stand alone)
The crew could see the whale. (complete
sentence)
Interactive example:
Mary is a fine singer, and
she is an excellent dancer. [show
me the dependent clauses]