How was helium first discovered?

mining of the radioactive element uranium
using spectral analysis of the suns’ emission spectra
hubble obtaining samples from explosions off the surface of the sun
deep sea mining off the coast of texas

It conforms what ever surface its in.

Hbr dissociates to form h+ and br-ca(oh)2 dissociates to form ca2+ and 2oh-the h+ and oh- react to form waterassuming the reactants are dissolved in water, the net reaction is h+ + oh- —> h2oif you’re asked to show all components of the reaction, the complete reaction is 2hbr + ca(oh)2 —> cabr2 + 2h2o

The image seems to be behind the mirror, but nothing is really there. if someone looks behind the mirror, there is no image there.