The rules that determine how sounds and words can be combined and used to communicate meaning within a language are collectively known as

Phonology.

Explanation:

Phonetics and phonology are two complementary branches of linguistics and their primary domain of study are sounds. Phonetics studies sounds as acoustic units, independent of their use and meaning.

The concern of phonology, on the other hand, are those same sounds as elements of a system that is a language. Phonology examines the way that sounds (phonemes) are used and combined in order to create meaning and transmit intelligible messages.

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the answer is b. the tomb is underground and dark, and its opening is covered by a heavy grate.