6. Conducting cells in phloem are a. Phloem parenchyma
b. Sieve tubes
c. Companion cells
d. Phloem fibres

B sieve tubes. The main conducting elements of the phloem are the sieve elements, of which there are two different types: sieve cells and sieve-tube members. Sieve cells have narrow pores, their sieve areas are quite uniform in structure, and they are distributed evenly on all walls.