Q: Fact 1: Vein deposits of gold and silver are formed by igneous intrusion. Fact 2: Magma that cools slowly deep below the surface produces coarse-grained intrusive igneous rocks. Given the two facts above, when do vein deposits of gold and silver form?

OPT:
a). When magma warms up;
b). flow of electrons;
c). it can be seen;
d). permineralization;
e). When magma cools;
f). aqueous solution;
g). When the air is cold;
h). When water rises;
The answer is:
e).