Question

how do nicotine and tobacco cause cancer?
by decreasing blood - sugar levels
by damaging or changing a cells dna
by increasing heart rate
by increasing phlegm and mucous production

Explanation:

To determine how nicotine and tobacco cause cancer, we analyze each option:

• "by decreasing blood - sugar levels": Blood - sugar level changes are not related to cancer causation by nicotine and tobacco.
• "by damaging or changing a cell’s DNA": Cancer is often caused by mutations (damage or changes) in a cell's DNA. Chemicals in tobacco (and nicotine - related factors) can cause such DNA damage, leading to uncontrolled cell growth characteristic of cancer.
• "by increasing heart rate": An increased heart rate is a cardiovascular effect, not a mechanism for cancer development.
• "by increasing phlegm and mucous production": This is a respiratory symptom (like in bronchitis - like conditions) and not related to cancer causation.

Answer:

B. by damaging or changing a cell's DNA