问题补充：
-Be careful! You might fall into the water.
-Thank you. I.I so close to the pool.
A. didn know; am standing
B. don know; am standing
C. didn’t know; was standing
D. didn know;Would stand
答案：
A. didn know; am standing
B. don know; am standing
(答案→)C. didn’t know; was standing
D. didn know;Would stand
解析：根据下文内容可知是之前没注意，用过去时，根据上下文的内容可知答案为C
