(a) 1:2
Least composite number = 4; least prime number = 2. HCF(4, 2) = 2, LCM(4, 2) = 4. Ratio of HCF to LCM = 2:4 = 1:2.
The least composite number is 4 (smallest number with more than two factors) and the least prime is 2. Students must recall these definitions clearly. HCF is the smaller (2) and LCM is the larger (4), giving ratio 1:2. A common mistake is confusing composite with even, or reversing the ratio.