太平天国运动兴起的最主要原因是：
A．阶级矛盾激化
B．外国资本主义侵略的加深
C．自然灾害严重
D．西方宗教思想的影响
A
本题主要考查学生对太平天国运动兴起原因的理解。1851年爆发的太平天国运动是鸦片战争后中国社会各种矛盾激化的产物。而腐朽的封建统治和沉重的剥削导致阶级矛盾激化，这是太平天国运动兴起的最主要原因，自然灾害严重、外国资本主义侵略的加深则加剧了阶级矛盾。
| Natural flavorings and fragrances are often costly and limited in supply. For example, the vital ingredient in a rose fragrance is extracted from natural rose oil at a cost of thousands of dollars a pound; an identical synthetic substance can be made for 1% of this cost. Since the early twentieth century, success in reproducing these substances has created a new industry that today produces hundreds of artificial flavors and fragrances. Some natural fragrances are easily synthesized; these include vanillin, the aromatic ingredient in vanilla, and benzaldehyde, the aromatic ingredient in wild cherries. Other fragrances, however, have dozens, even hundreds of components. Only recently has it been possible to separate and identify these ingredients by the use of gas chromatography and spectroscopy. Once the chemical identity is known, it is often possible to synthesize them. Nevertheless, some complex substances, such as the aroma of fresh coffee, have still not been duplicated satisfactorily. Many of the chemical compounds making up these synthetics are identical to those found in nature, and are as harmless or harmful as the natural substances. New products must be tested for safety, and when used in food, must be approved by the U.S. Food and Drug Administration. The availability of synthetic flavors and fragrances has made possible a large variety of products, from inexpensive beverages to perfumed soap to used cars with applied "new car odor." |
According to the passage, all the following are easier to synthesize EXCEPT ______.
A．aromatic ingredient in vanilla
B．vanilla
C．aromatic ingredient in wild cherry
D．the flavor of fresh coffee