The correct answer is (a) Practicability.
Accounting principles are generally based on practicability, which means that they should be easy to apply in practice. This is important because accounting information should be useful to decision-makers, and it is more likely to be useful if it is easy to understand and use.
The other options are not as important as practicability. Subjectivity refers to the fact that some accounting decisions are based on judgment, rather than on objective facts. Convenience in recording refers to the fact that some accounting methods are easier to record than others. Conservatism refers to the principle of erring on the side of caution when making accounting estimates.
Practicability is the most important principle of accounting because it ensures that accounting information is useful to decision-makers. Accounting information should be easy to understand and use, and it should be based on objective facts, rather than on judgment or convenience.