The center of mass is a point in a body where the mass of the body can be considered to be concentrated. It is the average position of all the particles that make up the body. In most cases, the center of mass lies within the body.

Option 1: A fountain pen - A fountain pen is a long, thin object with most of its mass concentrated towards one end. The center of mass is located within the body of the pen, closer to the heavier end.

Option 2: A cricket ball - A cricket ball is a spherical object with a uniform distribution of mass. The center of mass is located at the geometric center of the ball, which is well within the body.

Option 3: A ring - A ring is a circular object with a hollow space in the center. Since there is no mass in the center, the center of mass cannot be located within the body. In this case, the correct answer is option 3, where the center of mass lies outside the body.

Option 4: A book - A book is a solid object with a uniform distribution of mass. The center of mass is located within the body of the book.

Therefore, the correct answer is option 3, a ring, where the center of mass lies outside