
Those reaction in which two or more substances combine to form a one new substance are called Combination reaction
In this reaction, We can add :
- Two or more elements can combine to form a compound.
- Two or more compounds can combine to from a one new compound.
- An element and a compound can combine to form a new compound.


In this, Hydrogen is an element and Oxygen is another element. Both are combined to form compound 'Hydrogen oxide'. Hydrogen oxide is commonly known as water.
Electrical current is measured using the ampere.
Answer:
Kepler did and stated that planets move in a elliptical orbit with the sun in the center.