For something to be incessant, it means that it is continual.  For instance, an incessant noise indicates that the noise repeats itself.

"Inconvenient" is an adjective consisting of the negative prefix "in-" and "convenient," so we can infer that it means something like "not convenient"; it actually means "causing trouble, difficulties, or discomfort." So, we need to pick out an answer choice that means something like "not convenient" or "causing trouble." "Timely," then, cannot be the correct answer, because "timely" is an adjective that means "done or occurring at a favorable or useful time; opportune," making it an antonym, not a synonym, of "inconvenient." "Inopportune," however, is an adjective that consists of the negative prefix "in-" and "opportune," so it means "not opportune," or more specifically, "occurring at an inconvenient or inappropriate time." Because "inopportune" is the answer choice closest in meaning to "inconvenient," "inopportune" is the correct answer.

"Tardy" means late.

"Intermediate" means in the middle or in-between, so the best choice is "in-between" which also means in the middle. Don't confuse the word "meddle," which means to interfere, with the word "middle."

Something that is "chronic" continues for a long time. "Continual" is a synonym of "chronic." "Time" is not as good a choice because it refers to the general concept of time and not any length of time. "Old" also does not work here because it means great in age and does not refer to an ongoing process like the words "chronic" and "continual" do.

Seldom means rarely or not often happening, so "rarely" is the correct answer. To help you, "impressive" means demanding notice, striking, or great.

"Frequent" means happening again and again with little time in between events. Anorther word for "frequent" is often, so "often" is the correct answer. As for the other answer choices, "jealous" means envious or wanting what someone else has, "usually" means under normal circumstances, a "burrow" is a hole in the ground that certain animals dig and live in, and to "burrow" means to dig a hole in the ground, and "modest" means not taking as much credit as one should for one's achievements or talent.

Instantaneous means instant or occurring without any delay whatsoever. "Immediate" is the best answer choice because it also means instant.

The prefix "ultra-" means super or excessively, so “ultramodern” means extremely modern. Of the five answer choices, this is closest in meaning to “innovative,” which means original, modern, genius, offbeat. To provide further help, an “allusion” is an indirect reference to something; an “aqueduct” is a pipe that brings water from a natural source to a community; “assimilation” is the process of becoming part of a new culture after you move there; “apolitical” means not political, uninterested in politics. 

"Annual" means on a yearly basis, so "yearly" is the correct answer. "Kind-hearted" means nice and compassionate. "Difficult" means hard or tough to complete. "Stressful" means causing stress or anxiety. "Cooperative" means collaborative or working well with another person or others in a group.