3. The inner part of the potatoes and apples change in color because of
A. fuel in it
B. chemicals in it
C. exposure to heat
D. exposure to oxygen
4. The process of burning materials with the aid of oxygen is
A. conduction
B. combustion
C. oxidation
D. reduction
5. The Bureau of Fisheries investigated that fish kill incident was due to
A. lack of oxygen supply
B. hot summer temperature
C. use of illegal fishing methods
D. lack of carbon dioxide supply
6. The factors that influence the formation of rust on iron are
A, increased level of oxygen
B. moisture and cxygen
C. dropping of oxygen
D. oxygen level
7. The absence of oxygen in lighting a candle will cause the candle's flame to
A. burn
B. flare
C. ignite
D. extinguish
mi​