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:

Cancer is caused by mutations in a cell's DNA. Nicotine and tobacco contain carcinogens that can damage or change a cell's DNA, leading to uncontrolled cell growth and cancer. Decreasing blood - sugar levels, increasing heart rate, and increasing phlegm and mucous production are not direct causes of cancer.

Answer:

by damaging or changing a cell's DNA