If you get a flu shot one year why would you need to get it the next year ? why you aren't still protected from the flu ?

When elements that form a mineral dissolve in hot water, they form a mixture called a(n) a)geode b)vein c)evaporation d)crystallization e)magma f)lava g)solution h)gem

What is the identity of the planets?

Which step is not included in the step approach to calculating the greatest common divisor?