?一：blunt的反義詞是sharp，意思是鋒利的、尖銳的。

二：sharp通常用來形容物體的邊緣或者角度，也可以用來形容人的智慧和語言，表示思維敏捷、言辭犀利。

三：1. The knife's blade is sharp and can easily cut through the meat. 這把刀的刃很鋒利，可以輕易地切開肉。

2. She has a sharp mind and can solve problems quickly. 她頭腦敏捷，能夠迅速解決問題。

3. He made a sharp remark that offended everyone in the room. 他說了一句尖銳的話，冒犯了房間里的每個人。

4. The sharp turn in the road caught the driver off guard. 道路上突然出現的急轉彎讓司機措手不及。

5. The teacher's sharp criticism of the student's work motivated him to improve. 老師對學生作品的尖銳批評激勵他改進。

四：同義詞為keen，用法類似于sharp。：

1. He has a keen sense of humor and always makes us laugh. 他有一種敏銳的幽默感，總是讓我們笑。

2. The journalist has a keen eye for details and never misses any important information. 這位記者對細節有敏銳的洞察力，從不錯過任何重要信息。

3. The detective's keen observation skills helped him solve the case. 這位偵探敏銳的觀察力幫助他解決了這個案件。

4. She has a keen interest in art and spends most of her free time painting. 她對藝術有濃厚的興趣，大部分空閑時間都用來畫畫。

5. The company's keen business strategy has led to its success in the market. 公司敏銳的商業策略使其在市場上取得了成功。