Which one of the following characteristics is generally not preferred for a cloning vector?

The correct option is B Multiple restriction sites
Cloning vectors is a small piece of DNA into which foreign DNA fragments can be inserted for cloning purpose . Cloning vectors are used as functional origin of replication, selectable marker and gives a high number of copies. This may be a multiple cloning site which contains a unique restriction sites.

So, the correct answer is 'Option C' .