Which answer choice explains why furanoses and pyranoses can be reduced by sodium borohydride despite having no carbonyl functional groups.单项选择题

Furanoses and pyranoses cannot be reduced by sodium borohydride.

Sodium borohydride is a strong reducing agent, meaning that it can reduce weak electrophiles (such as hemiacetals).

Sodium borohydride is also a strong base, which converts hemiacetals to aldehydes/ketones.

Sodium borohydride is a weak reducing agent, meaning that it can reduce weak electrophiles (such as hemiacetals).

Mutarotation of these sugars leads to an intermediate sugar with aldehyde/ketone functional groups.