The answer is grow (i know you have an answer already. i just need points)
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The correct spelling of plurals usually depends on what letter the singular noun ends in. 1 To make regular nouns plural, add ‑s to the end. 2 If the singular noun ends in ‑s, -ss, -sh, -ch, -x, or -z, add ‑es to the end to make it plural.
Answer:
B. higher than the frequencies of radio waves.
