✨ ベストアンサー ✨
不定詞の副詞的用法:前の[形容詞]を修飾する
1) b) The math problem is [easy] to solve.
2) b) The computer manual is [hard] to understand.
3) b) Her handwriting is [impossible] to read.
4) b) This river is [dangerous] to swim in after the rain.
参考にしてください。