Step 1: Recall the different prestressing systems.
Among the prestressing systems:
- Freyssinet and Magnel-Blaton are post-tensioning systems.
- Hoyer's system is a pre-tensioning system widely used for factory production of precast structural elements.
Step 2: Identify the suitable system.
Since structural elements are mass-produced in precasting yards,
\[
\boxed{\text{Hoyer's system}}
\]
is commonly used.
Hence,
\[
\boxed{(C)}
\]
is the correct answer.