[多项选择]价值工程对象选择的方法有( )。
A. ABC分析法
B. 强制确定法
C. 百分比分析法
D. 因素分析法
E. 年数总和法

Are you interested in seeing the beautiful fall foliage of New England but tired of traffic jams and overbooked hotels Then this year forget the crowds in New England and see the beautiful colors of autumn in the Catskills.
These rugged mountains in New York State, just 90 miles northwest of New York City, are famous for the legendary tales of Rip Van Winkle, and more recently for the summer hotels mat sprang up in the region during the 1940s, 1950s, and 1960s. Families trying to escape the heat of New York City found the Catskills to be the perfect place to stay for a month or so each summer. By the late 1950s there were over 500 resorts and hotels offering nighttime entertainment as well as all kinds of outdoor activities. Famous comedies like Jackie Gleason, Joan Rivers, and Sid Caesar all got their start touring the hotel clubs here. Since the introduction of air-conditioning and cheaper air travel, however, families have stopped coming to the Catskills in such large
A. light and encouraging
B. informative and scientific
C. humorous and skeptical
D. regretful and reminiscent

在施工现场搭设了一个长6m、宽0.6m、高4.5m的一个现浇混凝土的梁模板，其支撑用的是Φ48和Φ51的两种型号钢管直接支撑在地面上，浇筑混凝土时，钢管沉陷，模板严重变形。
请判断事故原因。