The correct answer is (b).
A right in rem is a right that exists against the world at large. It is a right that is enforceable against anyone who interferes with it. For example, the right of ownership is a right in rem. If you own a car, you have the right to exclude anyone from using it without your permission.
A right in personam is a right that exists only against a particular person. It is a right that is enforceable only against that person. For example, the right to be paid a debt is a right in personam. If you owe me money, I have the right to sue you to collect the debt, but I do not have the right to seize your car or your house.
The options (a) and (c) are incorrect because a right in rem is not available against a particular person only or against the government only. It is available against the world at large.
The option (d) is incorrect because a right in rem does exist.