The first option. 100% correct.
[tex]a_n = 3\cdot a_{n-1}\\\\a_1 = 7\\\\a_2 = 3 a_{2-1} =3a_1 = 3(7) =21\\\\a_3 = 3 a_{3-1} =3a_2 = 3(21) = 63 \\\\a_4 = 3 a_{4-1} = 3 a_3 = 3 (63)=189\\\\7,21,63,189,......[/tex]
