Which of the following represents the largest man-made ecosystem?

An ecosystem that can be easily damaged but can recover after some time if the damaging effect stops,will have:

If a bamboo plant is growing in a forest,what will be its trophic level?

Classify the following ecosystems into their appropriate groups:
$I-$ Forest,$II-$ Grassland,$III-$ Pond,$IV-$ Desert
$V-$ Lake,$VI-$ Wetland,$VII-$ River,$VIII-$ Estuary
Terrestrial Ecosystem $\quad$ Aquatic Ecosystem

Where does the bulk of $CO_2$ fixation occur?

Keystone species are