第 11 至 15 題為題組     In certain forests, when you look up you will see a network of cracks formed by gaps between theoutermost edges of tree branches. It looks like a precisely engineered jigsaw puzzle, each branch growingjust perfectly so it almost,  11  , touches the neighboring tree. This beautiful phenomenon is calledcrown shyness.     Scientists have been discussing crown shyness since the 1920s, proposing  12  explanations forthe phenomenon. Some researchers point out that as trees often grow close together, treetops can easilycollide 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, andlight. In forested areas with thick tree crowns, there is intense struggle for these resources. Gaps in thetreetops resulting from crown shyness may allow trees to increase their  14  light and enhancephotosynthesis. Additionally, by having branches that do not touch those of their neighbors, trees may beable to limit the spread of leaf-eating insects, and potentially also the transmission of diseases from tree totree.  15  decades of investigation, there is no consensus on exactly what causes the beautiful andmysterious phenomenon of crown shyness.
【題組】11.
(A) in no time
(B) by all means
(C) but not quite
(D) and pretty much