Ahypothesis is question 20 options: a proven scientific fact an instrument that is used to examine environmental conditions a testable proposition that explains an observed phenomenon or answers a question the design of an experiment that can be used in scientific inquiry a prediction about something that has not yet been observed

The options are properly listed below:

A. a proven scientific fact

B. an instrument that is used to examine environmental conditions

C. a testable proposition that explains an observed phenomenon or answers a question

D. the design of an experiment that can be used in scientific inquiry

E. a prediction about something that has not yet been observed

ANSWER:

C. a testable proposition that explains an observed phenomenon or answers a question

EXPLANATION:

HYPOTHESIS is a proposed explanation for an observable fact, but that cannot satisfactorily be explained with the available scientific theories. It is based on the information acquired from a primary source or data collected during a scientific activity.

Also, for a hypothesis to be a scientific hypothesis, the scientific method requires that it is testable.

It is also a trial solution to a question.

Hypothesis can be provisionally accepted as a starting point for further research.

c

step-by-step explanation:

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.