The difference between a cell and a tissue is that tissue is made up of cells.
When a candle burns, energy is released in the form of light and heat.
Candles are used to provide light because when they burn, the energy which is released takes the form of light. Similarly, because fire is involved in the process, heat is given off as well.
It means that they are elements on the periodic table
I would probably say d because Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to reproduce.