50 points + brainliest
WRONG ANSWERS WILL BE REPORTED

i.  (answer is in the file I attached)  

ii. underground parts of the plants are thick , fleshy and swollen because they store food in the form of starch.

iii. Spines that have been converted into leaves. These prevent water loss by reducing surface area. The spines help defend the cacti from predatory animals. To decrease water loss due to evaporation, the cuticle is very thick and waxy.

iv. this plant is called a water lettuce it's leaves are modified to form modified to form hydrophyte They are aquatic plants that have evolved to thrive in water. This is capable of comprehending with aquatic macrophyte, which will be entirely submerged in water and in some circumstances allowed to float on the water's surface.  

hope this helps :)

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.