What is the definition of a lewis base?

B. A substance that donates electron to form a covalent bond

the answer to your question is c.

if you read the house of usher you should know that the house was haunted

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.