Growth rings are formed due to the activity of:

Growth rings are formed due to the activity of:
(A) Intercalary meristem
(B) Extra stelar meristem
© Primary cambium
(D) Interstelar meristem

Which of the following is formed by mesoderm of gastrula?

a. Central nervous system
b. Epidermis
c. Circulatory system
d. Liver and pancreas