Add comms where it is needed.
if there is no comma leave it alone.

1. rick had practiced his speech for hours but was still nervous when he got up in front of the class.
2. many college students would do well to cut back on their work schedule so that they can devote more time to their studies.

3. many people believe that a western-style democracy is not possible or practical in a country like china whose population is over one billion.

4. the geologist who lectured at browning hall last night predicted an earthquake in this area.
5. the old steam locomotives massive and powerful were an awe-inspiring sight.