Fatal reactions to bee stings among adults __________ than once believed.
举一反三
- Fatal reactions to bee stings among adults __________ than once believed. A: more are probably common B: more common probably are C: are more probably common D: are probably more common
- _________ that the earth was the center of the universe. A: People were once believed B: It had once believed C: People were believing D: It was once believed
- _______ that the earth was the centre of the universe. A: People were believing B: It was once believed C: People were once believed D: People were said
- Why do aldehydes undergo nucleophilic addition reactions while esters undergo nucleophilic acyl substitution reactions? A: The carbonyl carbon of an ester is more electrophilic than that of an aldehyde. B: Aldehydes are more sterically hindered than esters. C: Once the nucleophile adds to an aldehyde, the tetrahedral intermediate is too sterically hindered to eliminate one of the attached groups. D: Once the nucleophile adds to an aldehyde, neither H− nor R− can be eliminated since they are strongly basic.
- Exothermic reactions are faster than endothermic reactions.