The produces secondary phloem and xylem tissue, adding to a tree's girth.
a. vacuole
b. vascular cambium
c. meristem
d. xylem

The aswer is b. Vascular Cambium

it is a plant tissue which is located between Xylem and Phloem in the stem and root of a vascular plant and the source that produces Secondary xlem and phloem

Nb : Vascular Cambium does not transport waters , minerals, it only produce Xylem and Phloem which add the tree's girth

answer: - b cells

explanation: -

there are many types of white blood cells present in our body. one such class of white blood cells are the lymphocytes. the b cells belong to the lymphocyte class of wbcs. the b cells perform their action against the pathogen by producing specialised proteins called as antibodies. these antibodies are produced as and when the b cells encounter pathogens in response to the antigens present on the surface of the pathogen. these antibodies bind to the antigens present on the pathogen and then, target them for destruction by other cells of the immune system.

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.