Which statement most accurately describes the second law of thermodynamics?

a. energy cannot be changed from one form to another without a loss of usable energy
b. one usable form of energy can be completely converted into another usable form.
c. energy cannot be created nor destroyed but it can be changed from one form to another.
d. energy cannot be created or destroyed.
e. energy cannot be transformed.

Energy cannot be changed from one form to another without a loss of usable energy

Explanation:

Second law of thermodynamics states that the total entropy or the randomness of the system remains constant over time.  It also states that the net entropy will remain the same or it will increase.

Entropy of a system is given by heat absorbed divided by temperature. It is given by :

So, the correct option is (A) "Energy cannot be changed from one form to another without a loss of usable energy".

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.