Which statement is false ? A Nicotine inhibits release of adrenaline and nor-adrenaline. B Smoking is associated with increased incidence of many cancers.  C Smoking increases carbon monoxide content in blood. D Smoking reduces concentration of haembound oxygen.

The false statement is A: "Nicotine inhibits release of adrenaline and nor-adrenaline." In fact, nicotine stimulates the release of adrenaline and nor-adrenaline, which is part of the reason it can make users feel more alert and focused.

To determine which statement is false, let's analyze each statement one by one:

A) Nicotine inhibits the release of adrenaline and nor-adrenaline. This statement is true. Nicotine is known to inhibit the release of these neurotransmitters.

B) Smoking is associated with an increased incidence of many cancers. This statement is true. Numerous studies have shown a strong link between smoking and various types of cancer, including lung, throat, and bladder cancer.

C) Smoking increases carbon monoxide content in the blood. This statement is true. When tobacco is burned, carbon monoxide is released and inhaled into the lungs, where it is then absorbed into the bloodstream.

D) Smoking reduces the concentration of haemoglobin-bound oxygen. This statement is false. Smoking actually reduces the amount of oxygen that can bind to hemoglobin, leading to decreased oxygen levels in the blood.

Therefore, the false statement is D) Smoking reduces the concentration of haemoglobin-bound oxygen.