How to easily identify dependent clause?

Question

From the following sentences, which sentence contains a dependent clause?

1. Before taking the exam, my nephew studied really hard.
2. I heard something strange when downloading some movies last night.
3. The operator directly input the data after knowing about the repaired system.
4. That my father has worked as a network designer for five years is true

Is option (1) the correct answer?

I'm a beginner in English and I got confused a lot when it comes to identifying dependent clauses. I hope somebody can help. Thank you.

Answer 1

[1] Before [taking the exam,] my nephew studied really hard.

[2] I heard something strange when [downloading some movies last night].

[3] The operator directly input the data after [knowing about the repaired system].

[4] [That my father has worked as a network designer for five years] is true.

A dependent (usually subordinate) clause is one that is dependent on some other element in the sentence.

All your examples contain a dependent clause, each surrounded by square brackets.

In [1-3], the ing clauses are dependents of the prepositions "before", "when" and "after". In [4], the subordinate that clause is a dependent one by virtue of being a complement of the verb "be".

Note that traditional grammar takes "before", "when" and "after" as subordinating conjunctions; thus the clauses they introduce are subordinate , i.e. dependent ones.