I believe it's D. The centripetal force moves away from the center, but the marble stays there due to the string.
By definition, the density of an object is given by:

Where,
M: mass of the object
V: volume of the object
Since the mass and volume of an object are numerical values greater than zero, then it follows that:

It is important to respect the units of each measure.
For this case we can use the grams for the mass and cubic centimeters for the volume.
Answer:
A possible value for density is given by:

Answer:
C. microscope
Explanation:
A simple microscope is magnifying glass, an ordinary double convex lens having a short focal length that produces virtual and erect image.
1.COVALENT BOND [c] 2. Ionic bond [d] 3. Ionic bond [d] 4. a reaction where energy is released [b] 5. 2FE2C03=4FE=3CO2 [a] 6. The mass of reactant must be equal to the number of mass of the product [a] 7. Valence electrons [a] 8. Atomic number [a] 9. combustion [c] 10. More nitrogen in the nitrogen cycle [a]