Do all metal produce electromagnetic radiation when they are heated in a flame

Yes , all metals when placed in the heat produces EM radiations

Explanation:

Due to heat , the electrons mobilized and collapsed and electronic transition happened . the electrons shift from low level to high level and so on in the opposite . The electromagnetic radiation are emitted

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

i believe it is c.) 1575 j.