নিচের কোনটি 2-ইথাইল-3-ফরমাইল-পেনটানোয়িক অ্যাসিড?

$\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{CH}\left(\mathrm{C}_{2} \mathrm{H}_{5}\right) \mathrm{CH}\left(\mathrm{CO}_{2} \mathrm{H}\right) \mathrm{CHO}$

$\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{CHCH}(\mathrm{CHO}) \mathrm{CO}_{2} \mathrm{H}$

$\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{CH}(\mathrm{CHO}) \mathrm{CO}_{2} \mathrm{C}_{2} \mathrm{H}_{5}$

$\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{CH}(\mathrm{CHO}) \mathrm{CH}\left(\mathrm{C}_{2} \mathrm{H}_{5}\right) \mathrm{CO}_{2} \mathrm{H}$