Flat, gray clouds that cover most of the sky

Altostratus clouds are gray or blue-gray mid-level clouds composed of ice crystals and water droplets. The clouds usually cover the entire sky. Weather prediction: Be prepared for continuous rain or snow! Nimbostratus clouds are dark, gray clouds that seem to fade into falling rain or snow

Explanation:

not to sure sdi, strategic defense initiative

yup! you are correct it is b.