How many hydrogen atoms are represented in the formula (ch3)2ch2

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

Rocks, as they are compressed, begin forming mountains above the earth's surface when two continental plates converge. the continental crust increases in depth as the mountains grow above. the himalayan mountains formed at a convergent plate boundary in this manner. the rocks are smashed together causing them to due to the intense heat and pressure from the colliding plates and eventually forming rock. a) melt; igneous b) layer; sedimentary c) recrystallize; metamorphic d) melt into the earth's interior; metamorphic

What type of context clue you understand the meaning of  quandary?