B. Sound, because everything else sits still and sound waves move
Astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is as a binary star system.
<h3>What is the binary star system about?</h3>
A binary star system is known to be one where one star is known to be called a white dwarf and there is a mass that is said to be transferred to it
A binary star is known to be a kind of a system that is composed of two stars that are known to be gravitationally held together to and in orbit near each other.
Note that Binary stars in the night sky are ones that are often seen as a single object and thus Astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is as a binary star system.
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Answer:
(a) Most reactive 
Metal B
Metal D
Metal A
Least reactive Metal C
(b) (i) Bubbles should form very slowly
(ii) No reaction takes place
Explanation:
(a) The given metals arranged in their order of reactivity are;
Most reactive Metal B
Metal D
Metal A
Least reactive Metal C
The other of reactivity is based on the nature of their reactivity of the metals in air
(b) (i) Based on the reactivity of the metals in air, whereby metal A reacts very slowly and an oxide is formed, we have that, based on the reactivity of the metal A, when mixed with dilute hydrochloric acid, bubbles should form very slowly
(ii) Similarly, given that metal C is unreactive, we have that when small pieces of metal C are added to dilute hydrochloric acid, no reaction takes place.
Answer:
0.000001 kg
Explanation:
because 1 kg equal 1,000,000 milligrams
we take 
which equals 0.000001 kg
I think its all four of them could be wrong but try all four !!!!!!
