A sphere
sounds like a sphere to me.
A solid sphere perhaps?
That's a circle. The "fixed point" is the center of the circle, and the constant distance is its radius.
It is the locus of all points such that their distance from a fixed line (the directrix) is the same as their distance from a fixed point which is not on that line (the focus).
A circle is the set of all points in a plane that are a given distance (or a fixed distance) from another point. Take a plane, and then pick any point on it. Then pick a distance from that point you picked and connect all the points that are that distance from your fixed point. That will describe the circumference of a circle. Another idea is to take a plane, pick any point, and then take a compass and put the point of that instrument on that point you picked. Then set a distance on the compass and draw a circle. That circle will be that set of all points a fixed distance from the original point you picked. (A string will work as well as a compass if that string is not stretched to draw the circle.)
Sphere
sounds like a sphere to me.
A solid sphere perhaps?
This set of points forms a circle with the fixed point as its center.
That's a circle. The "fixed point" is the center of the circle, and the constant distance is its radius.
The center of the circle. That's how the circle is defined. (The collection of all points on a plane equidistant from a fixed point. The fixed point is the center and the fixed distance is the radius.)
CIRCLE
triangle
It is the locus of all points such that their distance from a fixed line (the directrix) is the same as their distance from a fixed point which is not on that line (the focus).
That's false
The question is ambiguous. Is the"single" point fixed or floating?
A circle is the set of all points in a plane that are a given distance (or a fixed distance) from another point. Take a plane, and then pick any point on it. Then pick a distance from that point you picked and connect all the points that are that distance from your fixed point. That will describe the circumference of a circle. Another idea is to take a plane, pick any point, and then take a compass and put the point of that instrument on that point you picked. Then set a distance on the compass and draw a circle. That circle will be that set of all points a fixed distance from the original point you picked. (A string will work as well as a compass if that string is not stretched to draw the circle.)