题干

压敏电阻的阻值随所受压力的增大而减小,有位同学设计了利用压敏电阻判断竖直升降机运动状态的装置,其工作原理图如图甲所示,将压敏电阻固定在升降机底板上,其上放置一个物块,在升降机运动的过程中,电流表示数如图乙所示,已知升降机静止时电流表的示数 I1 。下列判断正确的是(   )
                   甲                        乙

A:从0到 t1 时间内,升降机一定静止

B:从 t1t2 时间内,升降机可能做匀加速直线运动

C:从 t1t2 时间内,升降机运动时的加速度在变化

D:从 t2t3 时间内,升降机可能向下匀加速运动

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C

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    Wondering where to watch the fireworks on the fourth Friday of July? Here are some restaurants where you can sit, grab a bite to eat and watch the show.

    The Roof on Wilshire offers a view of the city, so chances are that you'll be able to catch a fireworks show while you're up there. The restaurant will also offer an all-you-can-eat menu for $20 that includes all beef hot dogs and sweet potato chips. The festivities will take place from 2 to 11 pm. Reservations are recommended. 6317 Wilshire Blvd. Los Angeles, (323) 852-6002.

    Whiskey Red's is located in Marina Del Rey. Beginning at 5:30 pm, it will include live music from Jack of Hearts. The event is free and open to the public. Guests can make reservations from 5:30 to 10 pm. It costs $59 to reserve a seat on the patio(露台) and $49 for indoor seating. Kids aged 5 to 12 need $25 for a seat outside and $20 for an indoor seat. Kids aged four and below are free. 13813 Fiji Way, Marina Del Rey, (310) 823-4522.

    High Rooftop lounge in Venice at the top of the Hotel Erwin offers views of the Venice coastline. The fireworks show starts at 9 pm. The rooftop lounge (休息室) offers a full menu of cocktails and a selection of snacks. 1697 Pacific Avenue, Venice Beach, (800) 786-7789.

    The last one is Carbon Beach Club at the Malibu Inn. Here you can see fireworks from a seat on the restaurant's oceanfront balcony from 6 to 9:30 pm. Reservations are recommended. 22878 Pacific Coast Hwy, Malibu, (310) 456-6444.