Pick the correct options :) sorry if it's hard...

1. Radius is ________________.
Options:
a. a chord
b. twice the diameter
c. a part of an arc
d. half of diameter

2.the distance between the center and any point on the circle is called its _____.
Options:
a. circumference
b. diameter
c. chord
d. radius

3. The diameter of a circle whose radius is 7cm is ______.
Options:
a. 21 cm
b. 44 cm
c. 3.5 cm
d. 14 cm

4. A dot (.) represents a _________.
Options:
a. line segment
b.line
c. ray
d. point