In fact, a visit to a major European city just would not be the same 16 encountering them: bathing in fountains, perching on historic buildings, and flocking in public squares.
答案：(D) without
without 是介系詞，後面接動名詞 encountering；would not be the same without… 意為「少了…就不一樣了」。as、though 當連接詞時後面必須接完整子句，for + V-ing 用於說明物品用途，都不合。
空格後面是 encountering，你一看到 -ing 就想找連接詞，把 as、though 填進去；但這裡的 -ing 是動名詞不是子句，需要的是介系詞。
空格後面是 encountering，是動名詞不是子句，所以這一格要填介系詞，不是連接詞。as 與 though 當連接詞時，後面必須接「主詞 + 動詞」的完整子句，這一句沒有，兩個可排除。for + V-ing 用來說明物品的用途：I need something for storing CDs.（我需要能收 CD 的東西），語意套不進來。剩下 without，後面正是接名詞或動名詞：without encountering them（沒有遇見牠們）、without saying a word（一句話也沒說）。整句是 would not be the same without…，意思是少了鴿子在噴泉洗澡、在廣場成群飛舞的畫面，歐洲城市之旅就不對味了。
would not be the same without…（少了…就不一樣了）、without doing sth（沒有做某事）、do without（沒有…也行）、cannot help doing（忍不住做）。其中 do without 這一組考過 3 個年度，101 年第 25 題 →、103 年第 24 題 →都出現過。
Street pigeons are a common sight in many European cities. In fact, a visit to a major European city just would not be the same 16 encountering them: bathing in fountains, perching on historic buildings, and flocking in public squares. In Barcelona, however, the birds are now threatening to 17 the city's historic center, pooping on monuments, buildings, and even tourists.
The city council originally proposed 18 the pigeon population by gathering the birds and shooting them. But that idea led to strong protests from numerous animal rights groups. After heated debates and discussions, the government was finally persuaded to consider another 19 effective method: giving the pigeons birth control.
In 2016, the city council decided to put its 85,000 pigeon population on a birth control pill to block the formation of eggs in birds. Starting from April 2017, the pills were placed in 40 bird feeders 20 throughout the city. It was predicted that there would be a decrease of 20 percent in the pigeon population in the first year and between 70 and 80 percent in four or five years.