13. 有一承受均佈載重之鋼筋混凝土簡支梁如圖(十)所示，試問在 a、b、c、d 四條裂縫中有那兩條是最可能產生在梁端之剪力裂縫？ (A) a 及 c (B) a 及 d (C) b 及 c (D) b 及 d

1. Lithium forms compounds which are used in dry cells and storage batteries and in high-temperature lubricants. It has two naturally occurring isotopes, 6Li (isotopic mass = 6.015121 amu) and 7Li (isotopic mass = 7.016003 amu). Lithium has an atomic mass of 6.9409 amu. What is the percent abundance of lithium-6? (A) 92.50% (B) 86.66% (C) 46.16% (D) 7.503% (E) 6.080%