Conservatism means:

a$)$not underestimating asset values, when faced with uncertainty about the value of assets and liabilities.

b$)$using the most optimistic measurement when faced with uncertainty about the value of assets and liabilities.

c$)$not overestimating liabilities, when faced with the uncertainty about the value of assets and liabilities.

d$)$using the least optimistic measurement when faced with uncertainty about the value of assets and liabilities.