It looks like a precisely engineered jigsaw puzzle, each branch growing just perfectly so it almost, 11 , touches the neighboring tree.
答案：(C) but not quite
almost, but not quite, touches 意為「幾乎碰到、但就是差那麼一點」，正是樹冠羞避現象的關鍵；in no time（立刻）、by all means（當然可以）、and pretty much（差不多）語意都不合。
答對率 29%。
句子裡已經有 almost（幾乎），你會覺得再補一句是多餘的，於是把 but not quite 排除。事實上 almost, but not quite 是一組固定的強調說法：almost 只說了「很接近」，but not quite 才把「就是沒到」這一點釘死——中文是「幾乎，卻又差那麼一點」。
全段在描寫 crown shyness（樹冠羞避）：樹枝彼此長得極近卻始終不相碰，中間留下細細的縫隙。第一句就寫 a network of cracks formed by gaps between the outermost edges of tree branches（樹枝末梢之間的縫隙所形成的網狀裂紋），下一句又說 This beautiful phenomenon is called crown shyness。整段的重點就是那個「沒碰到」的縫，所以非 but not quite 不可——若真的碰到了，這個現象就不存在。
in no time 是「立刻、很快」；by all means 是「當然可以、務必」，用於答應對方的請求；and pretty much 是「而且差不多」，與 almost 意思重複，也把「沒碰到」的關鍵抹掉了。
not quite 就是國中學過的 not really 那一類「部分否定」：I don't quite understand.（我不是很懂）、It's not quite ready.（還沒完全好）。quite 前面加 not，表示「還差一點才到」。
almost, but not quite（幾乎，卻差那麼一點）、not quite（不完全）、not exactly（不盡然）、in no time（立刻）、by all means（當然可以）。
In certain forests, when you look up you will see a network of cracks formed by gaps between the outermost edges of tree branches. It looks like a precisely engineered jigsaw puzzle, each branch growing just perfectly so it almost, 11 , touches the neighboring tree. This beautiful phenomenon is called crown shyness.
Scientists have been discussing crown shyness since the 1920s, proposing 12 explanations for the phenomenon. Some researchers point out that as trees often grow close together, treetops can easily collide and break when swayed by the wind. In order to protect their branches from breakage, trees maintain "shyness gaps"—spaces large enough to prevent them from touching their neighbors.
Other scientists suggest that plants, like animals, 13 resources—nutrients, water, space, and light. In forested areas with thick tree crowns, there is intense struggle for these resources. Gaps in the treetops resulting from crown shyness may allow trees to increase their 14 light and enhance photosynthesis. Additionally, by having branches that do not touch those of their neighbors, trees may be able to limit the spread of leaf-eating insects, and potentially also the transmission of diseases from tree to tree.
15 decades of investigation, there is no consensus on exactly what causes the beautiful and mysterious phenomenon of crown shyness.