| In a twin-tower desiccant type air dryer using silica gel as an adsorbing agent, what is the procedure for rejuvenating the tower presently on service when the desiccant becomes saturated with moisture? |
| A) The towers are shifted, and the off-going tower is refrigerated. |
| B) Heat is applied to the tower on service and it remains on service while heating. |
| C) The tower on service is refrigerated and it remains on service while cooling. |
| D) The towers are shifted, and heat is applied to the off-going tower. |
