Determine whether the underlined subordinate clause in the sentence below is an adjective clause, an adverb clause, or a noun clause. what caused the disruption of the online service remains a mystery.
a. noun clause
b. adjective clause
c. adverb clause

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).

hello,

this starts with

the areas residents asking congress for admission.

this is the first step in the process of admitting a new state,

- i.a -