The correct options are
A Cu-Be alloys are used in the preparation of high strength springs.
B Metallic beryllium is used for making windows of X-ray tubes.
D It is used in the manufacture of alloys.
Uses of Beryllium:
It is used in the manufacture of alloys.
Cu-Be alloys are used in the preparation of high strength springs.
Metallic beryllium is used for making windows of X-ray tubes.
Magnesium Carbonate MgCO3 is used as an ingredient in toothpaste.
So (a) , (b) and (c) are correct.