Which Is Correct? the General Rule Is That the Time by Which a by Which

Which is correct?
The general rule is that the time by which a defendant must file his defence is …

A) within the time agreed between the parties.
B) within 14 days after service of the particulars of claim.
C) within 28 days after service of the claim form if the particulars of claim had not been served at the same time.
D) within the time agreed between the parties provided that any extension agreed does not exceed 2 months extra time.