Read the text and fill in the gaps with the correct form of verbs. Microplastic particles (a) _______ (accumulate) in riverbed sediments that (b) _______ (enter) Bangladesh through India's Ganges river, (c) _______ (reveal) a recent study published in Elsevier's Ecotoxicology and Environmental Safety Journal. This study (d) _______ (mark) the first in Bangladesh to underscore the serious threat (e) _______ (pose) by microplastics in transboundary rivers to the marine ecosystem. It shows the role of rivers in transporting these microplastics into the marine system, (f) _______ (create) a potential threat to land, water and human health. The 330 kilometre journey from the Ganges river basin to the Meghna estuary (g) _______ (witness) the deposition of microlastics in shoreline water and deep sediments. According to the World Health Organization (WHO), microplastics are an "emerging" pollutant in environment which has a serious public health concern. Exposure to microplastic particles has human health implications when they enter the human body through the environment, food, water and air. Moreover, microplastics in water (h) _______ (float) or sink based on its concentration, duration and degradation rate of the materials. Chemicals associated with microplastics (i) _______ (be) also hazardous to aquatic life. The research (j) _______ (cover) 10 districts in Bangladesh, collecting a total of 180 water and sediment samples from 30 sampling points ( k ) _______ (stretch) from Chapainawabganj to Chandpur's Meghna estuary. The study (l) (reveal) that the highest concentration of microplastics (m) _______ (detect) near the Hardinge Bridge in Kushtia, while the lowest was at Premtoli Ghat in Rajshahi. The average microplastic concentrations in upstream and downstream water ( (n)_______( ) record ( ) ) at 24 to 50 particles per litre and 26 to 64 particles per litre, respectively.