Five sentences related to a topic are given below. Four of them can be put together to form a meaningful and coherent short paragraph. Identify the odd one out. Choose its number as your answer and key it in.

1. Ocean plastic is problematic for a number of reasons, but primarily because marine animals eat it.

2. The largest numerical proportion of ocean plastic falls in small size fractions.

3. Aside from clogging up the digestive tracts of marine life, plastic also tends to adsorb pollutants from the water column.

4. Plastic in the oceans is arguably one of the most important and pervasive environmental problems today.

5. Eating plastic has a number of negative consequences such as the retention of plastic particles in the gut for longer periods than normal food particles.