Let us think it a bit practically..
If we have modules having time complexities T1 and T2 , then time complexity of entire program = max(T1 , T2)
Keeping this in mind ,
Let T1 corresponds to f(n) and T2 corresponds to g(n) .h(n)..
So f(n) is guaranteed to be linear as f(n) = θ(n) ..
And g(n).h(n) if becomes larger than f(n) then the entire complexity becomes greater than function of n..It will have higher powers of n.So in that case it gives ω(n)..(Small Omega n)..
However if we have this product less than linear function of n , then we need not bother as f(n) is there to make for it..So in that complexity becomes θ(n)..
So considering the above two cases we can say that overall complexity or in other words the function f(n) + g(n).h(n) = Ώ(n)..Hence C) is the correct answer..