The correct option is D GP
Let two GP are
a,ar,ar2,ar3,ar4..... and b,bs,bs2,bs3,bs4,.....
Their multiplication is
ab,(ar)(br),(ar2)(br2),(ar3)(br3),.......
i.e. ab,ab(rs),ab(rs)2,ab(rs)3,.......
Clearly it is a GP with first term multiplication of first terms of both GP and common ratio is product of their common ratios.
Option C is correct.