One element isotope has exactly the same mass number and atomic mass. It was used as the definition of the atomic mass unit (amu). Which element isotope is it and what is its atomic mass?

hi,

the capital city of australia is canberra.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.