Questions

Rejuvenation occurs when the river’s base level falls (i.e. when sea level falls). This can be a consequence of either a fall in the amount of sea water or the land rising. Incised meanders are meanders which are particularly well developed and occur when a river’s base level has fallen giving the river a large amount of vertical erosion power, allowing it to down cut. Hence, 2nd statement is correct.

There are two types of incised meanders, entrenched meanders and ingrown meanders.As they are products of rejuvenation, they are not formed in mature stage of a river

Bioaccumulation is defined as the increase in concentration of a substance(s) in an organism or a part of that organism.

The affected organism has a higher concentration of the substance than the concentration in the organism's surrounding environment.

For the second statement: Microorganisms eat pesticide infected things. Invertebrates eat hundreds of the microorganisms and plants infected with the pesticides, accumulating a pretty large amount of the toxin in them.

The invertebrates are generally then eaten by larger invertebrates or amphibians, which ingest hundreds of similar organisms, accumulating an even higher concentration of toxins in their bodies. Then the fish eat hundreds of these organisms, accumulating the highest concentration of toxins in themselves.