These preparations are called Vaccines. A vaccine is a biological preparation that provides active acquired immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing micro-organism and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins.
D. an arctic fox is brown in summer and white in winter
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The classic symptoms of asthma include wheezing, coughing, tightness in your chest, and feeling short of breath. But other conditions — like allergies, chronic obstructive pulmonary disease (COPD), sleep apnea, and post nasal drip — can trigger the same problems.
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