保證正確率~！
正確答案是：D
解析：
If it hadn't been forthe expense, I would have takena round-the-world tour.
要不是因為經費問題，我早就去環球旅行了。A選項應該是 were it not for 才對，是對現在和將來的虛擬，省略了 if ，將 were 提前了。
B 選項也應該是 if it were not for 才對，也是對現在和將來的虛擬。
C選項的後半句不對，應該是 would take 才對，是對現在和將來的虛擬。
綜上所述，正確答案是D，這裏是對過去的虛擬。
不懂請追問，(*^__^*) 嘻嘻~~
望采納，祝開心~！！！