निम्नलिखित में से किसे सामान्य भौतिक विधियों द्वारा अलग किया जा सकता है?

Which of the following pairs can be separated by ordinary physical methods such as fractional crystallization?

The number of optically active stereoisomers for 2,3-dichlorobutane is:

Which among the following statements correctly describes a 'meso' stereoisomer?