"Corrugated" is an adjective that refers to a material, surface, or structure and means "shaped into alternate ridges and grooves." So, "flat" cannot be the correct answer because it is an antonym, not a synonym, of "corrugated." "Grooved," however, is an adjective that means "provided with or having a groove or grooves," and because it is the answer choice closest in meaning to "corrugated," it is the correct answer.

"Durable" is an adjective that means "able to withstand wear, pressure, or damage; hard-wearing," so we need to pick out an answer choice that means something like "able to withstand wear." "Fragile" cannot be the correct answer, then, because "fragile" means the opposite of "durable," so it is an antonym, not a synonym, of "durable." "Hardy," however, is an adjective that means "robust; capable of enduring difficult conditions" and because "hardy" is the answer choice closest in meaning to "durable," "hardy" is the correct answer.

"Firm" means hard.

"Vacant" means empty. "Empty" is the best choice because it is a part of the definiton for "vacant." Considering the other choices, "lively" means energetic, "absent" means away or missing, and "evacuate" means to leave an area because it is dangerous. "Evacuate" is not as good a choice because it is a verb, while "vacant" is an adjective.

The word "permeable" means full of small holes that let liquids and objects of a certain size pass through. The best answer choice is "porous," which means full of small holes that allow air or liquids to pass through. Considering the other choices, a "sponge" is something that is permeable, "permanent" means lasting forever and unchanging, and "changing" is an antonym of permanent. 

The correct answer is "rough." Both "rough" and "jagged" mean having a coarse, uneven surface. The other words all mean smooth, so they are antonyms, or opposites, of "jagged."

The correct answer is "digestible." "Edible" and "digestible" both mean able to be eaten. The other words have to do with food, but do not have to do with the ability of something to be eaten.

"Tepid" means moderately warm. The best choice is "lukewarm" because it also means moderately warm. Considering the other choices, "scold" means find fault with angrily and verbally, "clever" means intelligent or witty, and "deep" means extending far beneath the surface.

"Edible" means able to be eaten. Notice the suffix "-ible," which suggests that a word means able to be something. Watch for suffix and prefix patterns in English, as they can help you figure out the meanings of words you have not seen before.

"Dry" is defined as without moisture or liquid. Since "arid" climates are characterized as dry and having little rain, "arid" is the best answer choice. "Moist" is an antonym of "dry."