To understand this word, it is helpful to consider a word like "grateful." We are grateful for things that are pleasing to us. To be "grateful" is to be thankful for such pleasing things. The adjective "gratifying" means something akin to able to make someone grateful or thankful. Another way to put this is "pleasing," which is the best option among those provided here.

The word "terrain" is related to Latin roots meaning land or physical location. (For instance, think of the word "territory.") Now, the word "battlefield" might tempt you because we use the word "terrain" often when talking about warfare. Also, the word "mountain" is tempting, as it is a kind of terrain. However, the only word that simply means "land" is "ground". Think of when you say "the school's grounds." The word "ground" can refer in general to physical terrain. It is in this sense that it is an acceptable synonym.

The prefix or root word "port-" means related to moving or transporting, so a “porter” is another name for a “doorman.” For example, the person who collects your bags and holds the door for you at a hotel is considered a "porter." To provide further help, a “protector” is someone who defends someone else.

The Latin root "grat" means pleasing and is found in other English words like "gratitude" (thankfulness), "gratuity" (a tip given to a service worker to demonstrate your satisfaction as a customer) and "ingrate" (someone who is not thankful for something for which he or she should be thankful). The suffix "-ful" usually means full of (some emotion). Thus, it makes sense that “grateful” means pleased by and thankful for something. For example, if you had to move a lot of heavy furniture into a building that had no elevator, you would probably be very grateful if any of your friends offered to help you move.

"Flex" means bend and the suffix "-ible" means able to be, so "flexible" means able to bend or be bent easily, and "bendable" is the correct answer. “Rigid” is the opposite of “flexible"; it means strong, sturdy, and unable to have its shape changed easily; “stern” means very strict; “stable” means steady or unchanging; and "rough" means having a coarse and grating texture.

The suffix -spec means look so to "inspect" something is to look at it. "Love" is an emotion, and is not related on word level to "inspect." "Smile" and "laugh" are both things that you might do while inspecting something, but they're not actually related to the word in anything but an incidental way.

The prefix in- means not and the suffix -able means able to be. So, "incurable" means unable to be cured. This is closest in meaning to "deadly." Additionally, "probable" means likely; "edible" means able to be eaten; "envious" means jealous, wanting something that someone else has; "brainy" means clever. 

The suffix -ator means person who does. As in "protestor," which means person who protests or "demonstrator," which means a person who demonstrates against. These two words are synonyms. So, an "agitator" is someone who agitates. To "agitate" means to disturb, to cause trouble. The correct answer is therefore "troublemaker." Additionally, a "moderator" is someone who oversees a debate; a "guardian" is a protector, someone who protects.

The prefix a- means not and the suffix -theist means God. So, an "atheist" is someone who does not believe in God. This is closest in meaning to "nonbeliever." Additionally, a "deity" is a God; an "agnostic" is someone who is unsure as to whether or not God exists; a "fanatic" is someone who follows something passionately; an "editor" is a person who edits and makes decisions regarding the content of things like newspapers and magazines.

The suffix -ify means to make into. So, "purify" means to make pure. This is closest in meaning to "clean." Additionally, "revere" means deeply respect and admire; "improve" means make better; "detract" means take away from.