RAS question
Microplastics in the ocean are defined as plastic particles smaller than:
Correct answer: (A) 5 millimeters.
Microplastics in the ocean are plastic particles smaller than 5 millimetres in length.
Explanation
NOAA defines microplastics as small plastic pieces less than five millimetres long, roughly the size of a pencil eraser. That makes option A the exam-relevant threshold: the word "micro" is being used for a size class of plastic debris, not for metre-scale waste or microscopic-only particles. NOAA also explains why this definition matters in marine pollution: microplastics may form when larger plastic debris breaks down, or they may enter waterways as manufactured microbeads used in some health and beauty products. These particles can pass through water filtration systems and reach the ocean and Great Lakes, where they pose a potential threat to aquatic life. In broader exam context, microplastics are reported across oceans, soil, freshwater and even human blood, and are part of the global plastics-policy debate.
Why the other options are wrong
- (B) Five metres describes large marine debris, not the small plastic pieces NOAA classifies as microplastics.
- (C) Five centimetres is ten times larger than the five-millimetre ceiling used for the microplastic definition.
- (D) One micrometre is far below the standard microplastic cut-off and would point towards nanoplastic-scale particles rather than the NOAA definition tested here.
Concept
This tests the Environment and Ecology concept of plastic pollution, especially how pollutant categories are defined by size and source. It recurs in RAS because microplastics connect static ecology, current environmental governance and public-health concerns.