A compound noun contains two or more words that join together to make a single noun, like "keyboard." A compound noun is a type of compound word that is used to designate a person, place, or thing. Compound nouns can be formed in several ways, which is one reason why writing these words can be tricky.
Examples: noun + noun bedroom water tank motorcycle printer cartridge
noun + verb rainfall haircut train-spotting
noun + adverb hanger-on passer-by
verb + noun washing machine driving licence swimming pool
"<span>How many times greater is the acidity of hydrochloric acid than vinegar?" is the best option from the list, since this is what the chapter is primarily dealing with. </span>
I think the answer might be sad....
