The mass number of an element $$\mathrm{X}$$ is 175 with 104 neutrons in its nucleus. Into which one of the following orbitals will the last electron enter?

Bohr's radius of 2 nd orbit of $$\mathrm{Be}^{3+}$$ is equal to that of

The ion that is isoelectronic with $$\mathrm{CO}$$ is

A proton having mass equal to $$1.66 \times 10^{-27} \mathrm{~kg}$$ is accelerated to one tenth of the velocity of light. If its velocity can be measured to an accuracy of $$\pm 2 \%$$, what would be the uncertainty in its position?