Answer:
The correct option is C.
Step-by-step explanation:
The given expression is
[tex]21x-18x+28xy[/tex]
The factors of each term are
[tex]21x=3\times 7\times x[/tex]
[tex]18x=3\times 6\times x[/tex]
[tex]28xy=2\times 2\times 7\times x\times y[/tex]
The common factor is x.
[tex]G.C.F.=x[/tex]
Therefore correct option is C.
