已选分类
理学数学
单选题已知A，B，C均为圆上的点，问O是否为圆心?(1)AO=OB(2)A0=OC(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A four-character password consists of one letter of the alphabet and three different digits between 0 and 9, inclusive. The letter must appear as the second or third character of the password. How many different passwords are possible? (A) 5,040 (B) 18,720 (C) 26,000 (D) 37,440 (E) 52,000
单选题已知，其中f(x)连续，则f(3)=______。A.-2eB.2eC.-eD.e
单选题
单选题已知，μ，σ为实数且σ＞0，则=______。A．B．C．D．
单选题，A=αβT，则A的秩R(A)=______。A.1B.2C.3D.4
单选题有350个人，不是研究生就是本科生，从中任取一人，问是女研究生的概率为多少? (1)研究生有187 (2)女生有247
单选题Tom reads at an average rate of 30 pages per hour, while Jan reads at an average rate of 40 pages per hour. If Tom starts reading a novel at 4: 30, and Jan begins reading an identical copy of the same book at 5: 20, at what time will they be reading the same page? (A) 9:30 (B) 9:00 (C) 8:40 (D) 7:50 (E) 7:00
单选题(1)X＞0(2)X＜1
单选题当x＞0当时，曲线，则______。A.有且仅有水平渐近线B.有且仅有铅直渐近线C.既有水平渐近线也有铅直渐近线D.既无水平渐近线也无铅直渐近线
单选题当x→0时，下列函数为无穷大量的是______。A．B．cotxC．D．
单选题Exactly three years before the year in which Anna was born, the year was 1980 x. In terms of x, on Anna's twentieth birthday, the year will be
单选题Jolene began building a picket fence by planting stakes in a row; the stakes were evenly spaced. After planting the first 10 stakes, Jolene measured the length of the row and found that the row was 27 feet long. She continued the row by planting another 10 stakes, then measured the length of the entire row. How many feet long was the row of stakes Jolene had planted? (A) 37 (B) 54 (C) 57 (D) 60 (E) 81
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单选题Cansoftennisballswerepurchasedforthetournamentatacostof$1.90percan.Onlyofthecanswereusedforthetournament,sothe24unusedcanswerereturnedforarefund.Whatwasthecostofthecansoftennisballsusedforthetournament?(A)$34.20(B)$45.60(C)$60.80(D)$124.20(E)$136.8O
单选题设，则______。A．B．C．D．
单选题In a certain population, 40 percent of all people have biological characteristic X; the others do not. If 8,000 people have characteristic X, how many people do not have X? (A) 3200 (B) 4800 (C) 12,000 (D) 16,000 (E) 20,000
单选题设总体X服从参数为λ(λ＞0)的泊松分布，X1，X2，…，Xn+1为来自总体X的简单随机样本，记，则ET=______。A.λB.2λC.λ2D.2λ2
单选题9个整数构成等差数列，问其中项为几? (1)头7个中间项为13 (2)后7个中间项为17。
单选题Ifa=1and,whichofthefollowingisNOTapossiblevalueofb?(A)-2(B)-1(C)0(D)1(E)2