Answer: (3) silicon
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Silicon (Si)
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: ethane
, propanone
and water 
Answer:
They are pollinators of alfalfa.
Explanation:
Without them crops wouldn't be here.
Answer:
reactivity:very reactive,less reactive
density:float in water,sink in water
melting and boiling point:low,high
colour of salts: colourless,often coloured
I’m pretty sure it’s B since ones charge the neutral while ones is positive, it’s an obvious difference as well/