Certain ➡ sure, undoubted, fixed, regular, some
Cheap ➡ low and or reduced in price
Chemical ➡ actinic
Clear ➡ bright, not dark or obscured
Close ➡ near
Cold ➡ feeling the sensation of coldness, especially to the point of discomfort
Comfortable ➡ easy; relaxing; bringing comfort; financially well to do
Common ➡ simple, ordinary or vulgar
Competitive ➡ vying
Complex ➡ complicated