What is true of carbon atoms? they are not found in animals. they have five valence electrons. thy can form up to four covalent bonds. they do not bond with other elements

The answer is:  [C]:  "They can form up to four (4) covalent bonds."

   Note:  Think:  "HONC"  {"Honk"} ; 

      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). 

  "HONC" {"honk"} ;  1, 2, 3, 4 ;  in the order of the number of
                                          bonds they can form.