In general, which elements have the poorest thermal conductivity? a. metals
b. metalloids
c. nonmetals

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

sup bro, im dumb, but this is what i found xd

"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"