[单选题]
The image below is an electron mcgv 6.dn4x*h 1kxzo*r icrograph of(.yx9lfke:) aviy r0o the stem of the monocot Zea Mays.
What function is performed by the structure labelled X?
A. Transport of water from the roots to the leaves
B. Transport of organic compounds from sources to sinks
C. Transport of organic compounds from sinks to sources
D. Transport of water from sources to sinks