Final answer:
The element used in borosilicate glass, Boraxo soap, drill bits, and control rods in nuclear power plants is boron.
Step-by-step explanation:
The element used in borosilicate glass, Boraxo soap, drill bits, and control rods in nuclear power plants is boron (option A). Borosilicate glass is made by adding boron oxide to the glass composition, which makes it resistant to thermal shock. Boraxo soap contains borax, which is a compound of boron. Boron carbide is a strong and hard material used in drill bits. Control rods in nuclear power plants are often made of boron, cadmium, or hafnium to absorb neutrons and control the fission rate.