[1] when the twins grew up, they continued to fight. [2] one day they decided to hold a contest to determine who was
stronger. [3] though they tried to defeat each other in many different ways, neither one could win. [4] on the last day,
they fought with weapons. [5] after the right-handed twin chose a deer antler as a weapon, he overpowered his brother,
and he threw him off the edge of the earth. [6] today, the right-handed twin lives in the sky-world, and the left-handed
twin lives in the dark underworld. [7] they rule the earthly world of men together.
which sentence is a compound-complex sentence?

The correct answer is [5] After the right-handed twin chose a deer antler as a weapon, he overpowered his brother,  and he threw him off the edge of the Earth.

Explanation:

A compound-complex sentence is formed by two independent clauses and a dependent one. It's worth remembering that an independent clause  has a subject and a predicate and is capable of expressing a complete thought on its own. On the other hand, a dependent or subordinate clause is formed by a subject and a verb and starts with a subordinate conjunction or a relative pronoun. A subordinate clause does not express a full idea on its own; it needs the information expressed by the main clause in order to make sense. Dependent clauses commonly begin with words such as after, although, because, before, if, since etc.

Sentence 5 has two independent clauses and one dependent one. The first clause, "After the right-handed twin chose a deer antler as a weapon," is the dependent clause. It begins with after and needs more information to make complete sense. The other two sentences express complete thoughts on their own: "he overpowered his brother,  and he threw him off the edge of the Earth." They are joined by a comma and the coordinate conjunction "and".

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)