People with hypertension have a 60% greater risk of a heart attack when the temperature is more than five degrees cooler than the previous days temperature. As well as increasing blood pressure, cold weather can cause blood to thicken and make a clot more likely. Cholesterol levels also increase during cold weather and infections of the respiratory tract are far more common and contribute further to the risk of a heart attack. Hypertension is believed to affect 40% of adults in Northern Europe and very often goes unnoticed until serious damage to a sufferers health has occurred.

Question: Hyper tension can cause the blood to thicken and clot during a spell of cold weather.
Options:
A. true, B. false, C. uncertain
Answer: "B"