💡 Detailed Explanation
The correct choice is Option 2: 'Plain blue shirt.' The customer first requests a blue shirt ('青いシャツが欲しいんですが'). The clerk presents two patterns: checkered ('チェック') and plain ('無地'). The woman evaluates both: 'チェックはかわいいけど、仕事でも着たいから、無地の方がいいですね' (Checkered is cute, but because I want to wear it for work too, the plain one is better). Therefore, she purchases the plain blue shirt.