The answer is: [C]: "They can form up to four (4) covalent bonds."
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Note: Think: "HONC" {"Honk"} ;
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representing; the 4 (four) elements on the Periodic Table of Elements in the following order:
1) hydrogen (H) ; 2) oxygen (O) ; 3) nitrogen (N) ; 4) carbon (C).
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"HONC" {"honk"} ; 1, 2, 3, 4 ; in the order of the number of
bonds they can form.
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