To determine which number is divisible by 3, we need to know that if the sum of the digits of a number is divisible by 3, then the number itself is also divisible by 3.
Let's apply this rule to each of the given numbers:
a. 143: 1+4+3=8, which is not divisible by 3. Therefore, 143 is not divisible by 3.
b. 93: 9+3=12, which is divisible by 3. Therefore, 93 is divisible by 3.
c. 145: 1+4+5=10, which is not divisible by 3. Therefore, 145 is not divisible by 3.
d. 112: 1+1+2=4, which is not divisible by 3. Therefore, 112 is not divisible by 3.
Therefore, the only number that is divisible by 3 is option b, which is 93.