In which one of the following pairs, the two items mean the same thing?

Hemophilia is an X-linked recessive disorder and is characterized by impaired ability or inability of blood clotting which causes heavy blood loss even in the case of small injury. Pacemaker serves to produce rhythmic impulses for a heartbeat. The sinoatrial node (SA) node serves as a pacemaker. Malleus is one of the ear ossicles. Its shape resembles a hammer. Leucocytes refer to white blood cells and lymphocytes are just a type of leucocyte. That means all leukocytes are not lymphocytes. So the correct answer is option B.