The description of a process is usually done in steps, and can be more or less specific, depending on the audience. For instance, if you were going to write the process of ironing a silk shirt, you...
'this' is a determiner, it refers to
something you have already been talking about, "Oh! This is news to me!" something or someone that is physically near to you in contrast with something/someone...
Observe the process closely while taking notes. You might have to do this mentally, from memory, if you are not yourself performing the process or watching it performed, or by carefully reading other...
1-Type A ... which has antibodies : B ... and Antigene : A 2-Type B ... which has antibodies : A ... and Antigen : B 3-Type AB . which has No antibodies ... and has Antigen : A and B 4-Type O .....