题目

使用显微镜观察装片，在10倍物镜下观察到的图像清晰、柔和，再直接转换至40倍物镜观察。此时，除调节细准焦螺旋外，还需调节反光镜（或亮度调节钮）和光圈。正确的操作是（） A . 用平面镜（或调低亮度）、光圈缩小 B . 用平面镜（或调低亮度）、光圈放大 C . 用凹面镜（或调高亮度）、光圈放大 D . 用凹面镜（或调高亮度）、光圈缩小The National Air and Space Museum in Washington, DC has thousands of objects on display, including the 1903 Wright Flyer, Charles Lindbergh’s Spirit of St. Louis, the Apollo 11 Command Module Columbia, and a lunar rock you can touch. In addition to our exhibition galleries, you may want to visit the Albert Einstein Planetarium, Lockheed Martin IMAX Theater, and the Public Observatory on the east end. There are many things to do at the Museum in DC. We offer daily tours and educational activities for both children and adults. We also have scheduled lectures and events throughout the year.Hours & Admission: Open every day except December 25. Admission is free.Regular hours: 10:00 am to 5:30 pmExtended Hours: 10:00 am to 7:30 pmDecember 26— 30, 2015March 30—April 20, 2016Fridays and Saturdays, April 24—May 16, 2016May 17—September 7, 2015VISITING TIPS:Limit the Number of Bags: All visitors are screened through metal detectors upon entry. The fewer items you bring inside the Museum, the faster your entry. Before you visit, please review the list of prohibited items, which include pocket knives and tripods(三脚架). Visitors carrying prohibited items will not be allowed inside the museum, so please leave them at home or in your car.No food and Drink: Only bottled water is permitted in the Museum. You may only consume food and other drinks in the Food Court, not in the Museum. Groups who bring food are encouraged to picnic on the National Mall.Please Take Photos: You are welcome to take photos for personal use. However, tripods and monopods(单脚架) are not permitted without approval.]First Aid: The Museum has a First Aid office and a nurse on duty. Please contact the nearest security officer or the Welcome Center for assistance.Visit the Welcome Center: At our Welcome Center in the South Lobby, staff and volunteers can answer any questions you have during your visit.Phone: 202-633-2214E-mail: NASM-VisitorServices@si. edu1.According to the passage, the National Air and Space Museum is a museum _____.A. where only adults can take part in some educational activitiesB. everyone can pay a visit to without buying ticketsC. where one can touch anything he likesD. everyone can visit without time limits all the year round2. If the Greens plan to visit the Museum at 6:00 pm, it is accessible on ______.A. July 6, 2016 B. March 1, 2016C. December 24, 2015 D. September 15, 20163.What are the visitors allowed to take into the museum?A. pocket knives B. tripods C. bottled water D. monopods4.A visitor to the museum can _____.A. eat and drink in the Museum or in the Food CourtB. take photos with tripods for personal useC. bring fewer bags to go through metal detectorsD. get some medical treatment if he suddenly falls ill5.The purpose of this passage is to ______.A. make an advertisement for the museumB. attract people to explore the universeC. encourage adults to bring their children thereD. show what is on display in the museum