Nys, de
which statement is an identifying characteristic of a
mixture?
(1) a mixture can consist of a single element.
(2) a mixture can be separated by physical means.
(3) a mixture must have a definite composition by
weight.
(4) a mixture must be homogeneous.

Explanation:

For example, you can separate a mixture of sand and water by pouring it through a coffee filter.

(1) is wrong. A mixture must have at least two components.

(3) is wrong. A mixture can have a any composition depending on the amount of each component.

(4) is wrong. A mixture of sand and water is heterogeneous,

if you mean hydrogen and oxygen then water is the product

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.