All are true about cell theory except cells are structural and functional units of life
B All living things are composed of one or more cells
C most cells in humans are undifferentiated
D cells come from pre-existing cells

D: Cells come from pre-existing cells.

This cannot be true as some cells die, meaning they cannot come from pre-existing cells.

In regards to B and C most are undiffereniated and any living thing has at least one cell in them.

the organisms are not adapted to live in some communities or habitats.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds