Does anyone know the answer to this I need it ASAP

Which of the following is always a reactant in a combustion reaction? oxygen nitrogen hydrogen carbon

If the density of water is 1.0 g/cm3, which of these materials would float in water, based on their densities? check all that apply. aluminum cork iron lead wax

Ted and emily played a mixed doubles tennis match against jack and brenda. in the second match. ted and brenda played against jack and emily. which type of chemical reaction does the situation demonstrate?