How do cigarettes and radiation cause cancer? View Available Hint(s) How do cigarettes and radiation cause cancer? by destroying healthy cells by repressing the cell cycle by toxic chemicals (in smoke) or radiation that can damage the DNA in cells by destroying DNA by activating DNA mismatch-repair enzymes

B.  by toxic chemicals (in smoke) or radiation that can damage the DNA in cells.

Explanation:

The carcinogens presents in cigerates covalently bind to DNA and form DNA adducts which results into miscoding (e.g., insertion of the wrong base) during replication of DNA and this genetic mutation causes uncontrolled cellular growth which causes cancer.

Ionising radiation including X-rays, radioactive particles, and gamma rays,can cause cancer by damaging DNA. high-energy radiation damages DNA and cause genetic mutation same as cigerates and causes cancer.

Both toxic chemicals (in smoke) or radiation damages DNA inthe cells which leads to cancer.

Hence, the correct option is B.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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