单选题设，则dz=()

单选题将AABC各顶点的纵坐标加一3，连接这三点所成的三角形是由△ABC( )．

单选题设(an}是等比数列，an＞0(n＝1，2，…)，记An＝(lnSn+lnSn+2)，Bn＝lnSn+1，则对一切n(n≥1)有()．

单选题问19个数的中数(median)? (1)最大的14个数都是9； (2)最大的4个数都大于8。 (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．

单选题设直线ι方程为：，平面π与它垂直，则下列说法正确的是()。A．直线ι的方向向量与平面π的法向量垂直B．直线ι的方向向量与平面π的法向量平行C．平面π的法向量是1，2，3D．直线ι不经过原点

单选题在平面直角坐标系中，若点P(x-2，x)在第二象限，则x的取值范围为( )．

单选题{{B}}Directions:{{/B}} There are 4 reading passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C, and D. You should decide on the best choice and mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets. One of the youngest independent countries in the Western Hemisphere, Trinidad and Tobago, became a nation on August 31, 1962. For a long time this nation has attracted tourists--it is the home of calypso music and limbo dancing--and in recent years its healthy economy has attracted investors as well. Trinidad and Tobago is a single country composed of two islands: Trinidad, with the majority of the country's 900,000 inhabitants, is a rectangle of roughly fifty by forty miles. Tobago, nineteen miles to the north, is smaller and has a population of about 35,000. Situated at the end of the long chain of Windward and Leeward Islands, Trinidad is at one point only seven miles off the coast of Venezuela. Its geology, flora, and fauna are similar to those of the South American mainland. Like Venezuela, the backbone of Trinidad and Tobago's economy is petroleum and its first colonists were Spaniards. Three mountain ranges, with summits of up to 3,000 feet, cross Trinidad from east to west, while Tobago is a relatively flat coral island, rimmed with fine beaches. The broad plains between Trinidad's mountain ranges are dominated by vast fields of sugar cane that present a symmetrical green pattern when seen from the air. A closer inspection reveals the coconut plantations along the coast and the profusion of brilliant red and yellow flowers of various species that are found all over the island. Houses on both islands tend to be light-colored, with an open style of architecture, in many cages with open space under the entire dwelling. Port-of-Spain, the capital, is a bustling modern city where the pulse of the people reflects Britist, Spanish, and East Indian influcnces.

单选题设a1，a2，a3，a4成等差数列，且a1，a4为方程2x2-5x+2=0的两个实根，则a2+a3=______。A．B．-1C．1D．

单选题下列各式中正确的是()．