11. 木質加工板用熱壓貼表面材料，有時會爆裂是因 (A)板料含水率太高 (B)板料含水率太低 (C)溫度太低 (D)板料密度太大。

Problem of 1and 2:Three identical stars, each star's mass is M, form an equilateral triangle that rotates around the triangle's center as the stars move in a common circle about that center. The triangle has edge length L. (The gravitational constant is G)1. What is the net force on each star?(A)2(GM²/L²) (B)(C)(GM²/L²)/2 (D)(E)None of the above