What is an AUV? What's a 'big obstacle' of using robots in the deep ocean?

What do scientists use instead of 'radio waves' to keep in touch' with AUVs?

Part of molten rock at mid-ocean ridges

Which of the following true? a_volcanoes and earthquakes often near the plate boundaries. b_volcanoes occur whereve there are tall mountains. c_earthquakes cause volcanoes in the same location to erupt violently d_volcanoes and earthquakes occur only where plates are colliding with each other

Word equation for k(s)+h2o(l) yield koh(aq) + h2(g)