Concept: Carbon neutrality means balancing the amount of carbon dioxide emitted with the amount removed or offset, so that the net emission becomes zero.
Step 1: Understanding net carbon emission.
Net carbon emission is calculated as:
\[
\text{Net emission} = \text{Total emission} - \text{Carbon removed or offset}
\]
Step 2: Applying the condition given in the question.
The question says that net carbon emission in a year is zero.
\[
\text{Net emission} = 0
\]
This means the released carbon is balanced by removal, absorption, or offsetting.
Step 3: Matching with the correct term.
Carbon credit is a permit or certificate related to emission reduction.
Carbon sequestration is the process of capturing and storing carbon.
Carbon leakage means shifting emissions from one place to another.
Carbon neutral means net zero carbon emission.
Therefore, the correct answer is Carbon neutral.