Why is the thymus gland considered part of lymphatic system?

why is the thymus gland considered part of lymphatic system?
a) secretes hormones
b) site of T cell maturation c) secretes lymphatic fluid
d) filters and removes dead red blood cells
e)site of stem cells for blood

and question 2

Patients who have recently been exposed to hepatitis virus can be given an intravenous injection of immunoglobin what does this do?
a) provide long term preotection from hepatitis
b) prevent patient from transmiting virus
c) confers passive immunity to disease
d) stimulate formation of memory B cells
e) stimulates patient to produce own set of antibodies to hepatitus virus

please only answer if you know the answer dont just guess

thanks