Which two formulae correctly show a pair of structural isomers?
- A$\text{CH}_3\text{CH(CH}_3)\text{COOH}$ and $(\text{CH}_3)_2\text{CHCOOH}$
- B$\text{CH}_3\text{CH(COOH)CH}_3$ and $(\text{CH}_3)_2\text{CHCOOH}$
- C$\text{CH}_3\text{CHCOOH}$ and $\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}$
- D$\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}$ and $(\text{CH}_3)_2\text{CHCOOH}$