Which is the heavier one? 

The correct answer is: D

Step by step solution:
Let us first analyze the options carefully.
option(a) is a picture of a plastic scale which might weigh around 10-15 grams
option(b) is a picture of a comb which might weigh around 20-30 grams
option(c) is a picture of a metric weight which should weigh 1 kg
option(d) is a picture of a bicycle which might weigh around 5-10 kg.
Hence, we come to a conclusion that the heaviest among the 4 pictures given is the bicycle.
Hence, option(d) is the correct option.