Why is water hyacinth called the 'Terror of Bengal'?

Given below are two statements $:$
Statement-$I$ : Species facing competition might evolve mechanisms that promote co-existence rather than exclusion.
Statement-$II$ : In endoparasites,morphological and anatomical features are greatly simplified while emphasising their reproductive potential.
In the light of the above statements,choose the correct answer from the options given below.

The following graph depicts changes in two populations ($A$ and $B$) of herbivores in a grassy field. $A$ possible reason for these changes is that

Select the statement which explains best parasitism.

While explaining interspecific interaction of population,$(+)$ sign is assigned for beneficial interaction,$(-)$ sign is assigned for detrimental interaction and $(0)$ for neutral interaction. Which of the following interactions can be assigned $(+)$ for one species and $(-)$ for another species involved in the interaction?

If the '$+$' sign is used for a beneficial interaction,the '$-$' sign for a detrimental interaction,and the '$0$' sign for a neutral interaction,then which population interaction is represented by '$+$' and '$-$'?