Question

a A piece of music sung
sung or played
played in the open air​

Answer 1

Ignition temperature is an important property of any fuel because the combustion reaction of the fuel becomes self-sustaining only above this temperature. ... When the fuel is heated by some external means, the rate of exothermic reaction increases with a corresponding increase in the heat generation rate

Answer 2

Answer:

Serenade

Explanation:

Serenade: a piece of music sung or played in the open air, typically by a man at night under the window of his beloved.