The correct matches are:
a. measured on the Richter scale - Earthquake;
b. lava comes out - Volcano;
c. natural hazard - Both;
d. caused by subduction - Both;
d. forms a mountain - Volcano;
e. occurs underwater - Both;
f. measured using a seismograph - Volcano;
The earthquakes and the volcanoes go hand by hand together in lots of cases, mostly where there's subduction zones. In fact, the volcano activity is more often than not, causing earthquakes. They appear on the edges of the plate boundaries, and are cause by the movement of the tectonic plates, and the pressure, temperature, and magma from the Mantle layer bellow.
