What is the name of the structures that move substances across a tract surface?

cilia and flagella

Explanation:

In prokaryotic species , cilia are present , and in eukaryotic species , flagella is present .

Cilia and flagella both have same function , i.e. , to enable the movement of the cell , along with the movement of some substance and direct the flow of these substance along the tracts.

Cilia and flagella are composed of basal bodies.

Hence , from the given statement of the question,

The correct term is cilia and flagella .

Covalent bonding

Explanation:

Sulfur Dioxide is a process of covalent bonding, since Sulfur and Oxygen are both non-metals. The Sulfur is in the center surrounded by 2 Oxygen atoms.