Past perfect Vs. Simple past

[bayou_3034]

Qtn:
<The scientist knew for a long time beyond a shadow of a doubt> that she discovered the double helix.

C) For a long time, the scientist had known with great certainty

D) For a long time, the scientist knew beyond a shadow of a doubt

Can you please provide your explanation for choosing one over the another?

Thanks

[merlinacious]

I would choose D.
There are 2 actions, DISCOVERED and "known". The discovery took place after which she knew.
If more than one action has occured at different times in the past, you must use Past Perfect for earlier action and simple past for later.

So knew would be a better option over HAD known as know is not the earlier action.
Please post the Official Answer.

[Razind]

Past perfect is used only when it denotes an action which happened before another action in the past.

eg

This incident had happened before he was born.
In the example provided there is no reason to indicate that there is any action that happened before the discovering of the helix.

Tha action of knowing happened only after the helix was discovered
Hence the the use of past perfect is not justified.

Hence C cannot be correct

which leaves D which has to be correct.

[casperGasper]

I would choose D.
If more than one action has occured at different times in the past, you must use Past Perfect for earlier action and simple past for later.

I agree there are 2 actions here:
1) Knowing (about the discovery)
2) Discovering

Thus, the action "knowing" happened before discovering.
for this argument, why cannot C be right?

I choose C.
Official Answer?

[Divin]

Would go for D - simple past

[zombie_in]

Imo D.

[geekybiz1]

My pick - D

[shud]

Even D doesn't seem good but C is incorrect for sure.

[bayou_3034]

Official Answer is C.
Can anyboby explain - how?

[amitg_ind]

Official Answer has to be C.
Scientist knew about it long time back implies that this action Official Guide 'knowing' is before actual 'discovering'.