Explanation: 1 gram equals to 100 centigrams. We can also say that, 1 centigram equals to 0.01 gram.
From above centigram to gram conversion factor, there are two decimal places in 0.01 gram. So, a centigram balance is the one that could read the mass of a matter(object) to two decimal places.
Balance A can only read to one decimal place where as balance B can read the mass up to two decimal places.