Your advice would be ________ valuable to him, who is at present at his wit's end.
句意：你的建议对他是很有价值的，他现在已经智穷才尽了。exceedingly极其，非常。excessively过分地，过度地。extensively 广阔地。exclusively唯一地；排外地。因此，本题的正确答案为A。