请问LSAT-1-4-17, LSAT-1-4-18,LSAT-1-4-23

If the artificial is not better than the natural, to what end are all the arts of life? To dig, to plow, to build, to wear clothes—all are direct violations of the injunction to follow nature.

17.   Which one of the following is an assumption made by the author of the passage?

(A) The arts of life have no useful end.

(B) The artificial is not better than the natural.

(C) Digging, plowing, building, and wearing clothes are better than nature.

(D) The injunction to follow nature should not be violated.（C）

(E) The arts of life are indirect means of following nature.

18.   If the author’s argument were challenged on the grounds that the construction of buildings has adverse effects on the natural environment, which of the following replies might the author use to respond to the challenge logically?

(A) There are human activities, such as making music, that are environmentally harmless.

(B) Harming the environment is not an end, or purpose, of the arts of life.

(C) The construction could involve the use of natural, not artificial, materials.

(D) Constructing buildings is not an “art of life.”（E）

(E) Even if the natural environment is disturbed by the construction of buildings, it is improved for human use.

Just as a bicycle chain may be too tight, so may one’s carefulness and conscientiousness be so tense as to hinder the running of one’s mind.

23.   Which one of the following most closely parallels the reasoning used in the argument above?

(A) Just as a clock may be wound too tightly, so may one’s time be spent fruitlessly in the pursuit of perfection.

(B) Just as a carousel may spin too quickly, so may one’s rapid concentration on several problems prevent a resolution of difficulties.

(C) Just as a machine may be oiled too much, so may one’s heavy drinking of alcoholic beverages lead to complete dissipation.

(D) Just as a raging river may be frozen into stillness during the winter, so may one’s career falter at certain times of the year.（B）

(E) Just as a boxer may become too tense before a big fight, so may one’s personal concerns stand in the way of professional success.

这几道题的题意我都不是很清楚，更不要说作出答案了，请各位NN多指教！