If a vaccine protects you for most of your life against a particular pathogen, why do you need a new flu shot every year? A. Influenza evolves very quickly and its antigens mutate so that your memory cells from the last vaccine won’t recognize it. B. Influenza is so strong that you need a booster every year to make sure your body can fight it. C. Influenza is a virus, and vaccines only generate memory cells for bacterial infections. D. You don’t need it every year, it is just offered every year for anyone who does not have it yet.

Grade 91.)the gravitational pull from the moon words).2.) what is the rate of gravitational 3.)if you drop a hammer, is it more likely to drop handle side down, head side down, or equal chance that it will land either way? why? 4.)a car moves 60km east and 90km west.a.) what is the distance the car traveled? b.) what is the car's displacement5.)what is the average velocity of a car that moved 60 km south in 3 hours? 6.) a car starts from rest and acceleration to 60 m/s over a time of 5 seconds. what is the acceleration of the car? 7.)what is the speed of an object at rest?