If the viscosity of a magma is high, the magma is more likely to

a)make dark colored rocks.
b) contain trapped gasses.
c) contain relatively small amounts of silica.
d) lead to a non-explosive eruptions.

b) contain trapped gasses

Explanation:

The highly viscous magma is a magma that has high content of silica, and high content of gasses. There's two types of magma that have these characteristics, intermediate (andesitic) and felsic (rhyolitic). The high content of silica makes the magma highly viscous, and that composition actually traps the gasses inside the magma. As the magma rises toward the surface, the pressure and temperature change, resulting in explosion of the trapped gasses, thus creating explosive and effusive eruptions. Through this eruptions, the volcanoes shot out lot of pyroclastic material, making their surroundings very dangerous.