What are two ways floods can be controlled?

One of the ways is to construct dams across rivers that store water so it doesn't spill onto the adjacent land.

Another way is to construct levees, which are lateral walls along a river. The levees confine the rivers to the channels, so the river doesn't spill onto the adjacent land.

Another way is to build a sea wall, revetment, or bulkhead along the coast to keep excessive high tides from spilling onto the adjacent land. Salt marshes also serve to help reduce excessive high tides from spilling onto the adjacent lands.  

c is the correct answer!

the correct answer is option d.

an appositive is a noun, noun phrase or noun clause which follows another noun or noun phrase in order to describe it or name it another way. they are usually used between commas, brackets or dashes.

the example sentence with the correct use of commas is the following:

her uncle, the man over there in the red shirt, owns the hardware store in town.