Which statement should he place in the region marked x

Given: circle a externally tangent to circle b. how many possible common tangents to circles a and b can exist? 2 3 4

When volcanoes erupt, magma (hot, molten rock) rises toward the surface of the earth. as magma cools, solid rock forms. this rock contains substances from the interior of the earth. which of the following natural resources is likely to be plentiful near subduction zones where volcanic activity has occurred in the past?

The graph below plots the temperature and luminosity of stars on the main sequence.