Answer:
<em>Which statement is true about the activity series? </em>
Elements are listed according to their reactivity. This allows you, in a displacement reaction, to deduce if a reaction is going to take place accordingly to the reactivity of the reactants.
<em>Which of the following statements is true about nuclear fusion?</em>
It occurs in the sun. In fusion, nuclei of lighter atoms are combined to make a heavy nucleus, and it release a large amount of energy.
<em>Which of the above reactions is an example of a combustion and also a synthesis reaction?</em>
1 C3H8 + 5O2 → 3CO2 + 4H2O
Here a fuel (propane, C3H8) reacts with O2 to produce heat, carbon dioxide and water. And those are the characteristics of a combustion reaction.