The correct answer is: B. Where the endorser only signs without writing any name on the instrument.
An endorsement in blank is an endorsement where the endorser only signs their name on the back of the instrument. This type of endorsement makes the instrument payable to bearer, which means that anyone who has possession of the instrument can negotiate it.
Option A is incorrect because an endorsement in blank does not require the endorser to write anything on the instrument other than their signature.
Option C is incorrect because an endorsement in blank does not require the endorser to write the name of the person who is directed to pay.
Option D is incorrect because an endorsement in blank is a valid type of endorsement under section 16 of the Negotiable Instrument Act.