You don't know ______ I want to see you again. It's a year since I last saw you.
A:how soon
B:how long
C:how much
D:how often
水果店原有35筐桔子,又运进65筐,后来卖出了48筐,水果店现有桔子多少筐?
根据人的体貌特征,世界上的人类主要分为三大人种。形成人种差异的主要因素是( )