How is the noun clause used in the sentence?

why the group had gathered at the mall was a mystery.

a. direct object

b. object of a preposition

c. subject

d. indirect object

The noun clause are used in a sentence by a group of words acting together as a noun. These clauses are always dependent clauses. That is, they do not form a complete sentence.

Indirect object

Explanation:

Because it suppose to have a question mark after mall and a exclamation mark.

honestly, school in itself just seems to be a huge waste of time. a lot of people graduate but still end up not doing anything in college anyways, which really makes the whole point of graduating seem useless. i'd rather not bring anyone's hopes up then. what i'd recommend is for whoever's reading this to simply drop out.

i mean, kanye did it. he said something along the lines of, "don't let society tell you what to do." now, he's obviously a very successful person, and since his album is called the college dropout i guess he never really had to go through all that nonsense in order to become a millionaire. the same goes for anyone else then.

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).