题目

In the Caucasus region of Russia, nearly 50 out of every 100,000 people live to celebrate their 100th birthday, and many don’t stop at 100! By comparison, in America only 3 people in 100, 000 reach 100. But these Russian old people aren’t alone. The Pakistanis, who live high in the Himalaya Mountains, and the Ecuadorans of the Andes Mountains seem to share the secret of long life, too. These people remain healthy in body and spirit despite the passage of time. While many older people in industrial societies become weak and ill in their 60s and 70s, some Caucasians aged 100 to 140, work in 如图所示，F1为电线对电线杆的拉力（保持不变），F2为防止电线杆绕O点倾倒的攀绳产生的拉力，请画出F2的力臂L2。为了更安全，应                 （填“增大”或“减小”）角α 。