单选题 Simon's letter was in such a casual scrawl, and in such pale ink, that it was ______.
A. vague B. ambiguous C. illegible D. obscure

【正确答案】 C
【答案解析】vague含糊的，不清楚的；ambiguous模棱两可的，不明确的；illegible难辨认的，字迹模糊的；obscure模糊的，晦涩难懂的。