standard candle..correct usage of tense

[rahulg83]

A "standard candle" is a light source whose intrinsic luminosity is so well known that the extent to which its brightness has been dimmed by distance can be used as an astronomical yardstick

A) so well known that the extent to which its brightness has been dimmed by distance can
B) so well known that the extent of its brightness that is dimmed by distance can
C) sufficiently well known so that the extent that distance has dimmed its brightness can
D) sufficiently well known for the extent of its brightness that has been dimmed by distance to
E) sufficiently well known for the extent that distance has dimmed its brightness to

Between A and B, which is better? I am confused about the usage of tense here.

[California4jx]

A "standard candle" is a light source whose intrinsic luminosity is so well known that the extent to which its brightness has been dimmed by distance can be used as an astronomical yardstick

A) so well known that the extent to which its brightness has been dimmed by distance can
B) so well known that the extent of its brightness that is dimmed by distance can
C) sufficiently well known so that the extent that distance has dimmed its brightness can
D) sufficiently well known for the extent of its brightness that has been dimmed by distance to
E) sufficiently well known for the extent that distance has dimmed its brightness to

Between A and B, which is better? I am confused about the usage of tense here.

I think - B - is better.

A - is using has been - which is wrong in this tense/scenario
B - using simple past.

[subha_sri8]

I think A is better as the correct idiom is "extend to" and not "extend of"

[Domnu]

I think the answer A is better, because B suggests that extent of brightness is dimmed by the distance, which makes no sense.

[rs2010]

A gives correct meaning and has been is necessary to get the clear idea.
extent of is precise.