Secondary active transport is a process by which molecules are moved against their concentration gradient using energy indirectly.
The key driving force behind secondary active transport is an electrochemical gradient that has been established by primary active transport.
In primary active transport, ATP is directly used to pump ions across the membrane, creating a gradient of ions, usually sodium or hydrogen ions.
Secondary active transporters then harness the energy stored in this ion gradient to co-transport other substances either into or out of the cell.
This means that while the secondary transporter itself does not hydrolyze ATP, it relies on the ion gradient generated by primary active transport to move molecules against their concentration gradient.

The other options are incorrect because:
Option 2 describes primary active transport, where ATP is hydrolyzed directly by the transporter.
Option 3 refers to facilitated diffusion, which is passive movement down a gradient and does not require energy.
Option 4 describes passive diffusion, which occurs through the lipid bilayer without protein assistance and does not require energy.

Therefore, the correct mechanism driving secondary active transport is an electrochemical gradient generated by primary active transport.

Reference: Ganong's Review of Medical Physiology, 26th Edition, Chapter 3: Membrane Transport