But is used to introduce a word or phrase that contrasts with what was said before. Here first sentence is in contrast to the second part. Hence but will be filled in this blank.

The meanings of these phrasal verbs are as follows:

Do over means to do something again.

Do away with means to discard.
 
Do up means to make something look good.
 
Do without means to live or manage without something or someone.
 
So, the correct phrasal verb which makes sense in the given sentence is “do away with” as the mother is asking to discard the old records.

The meanings of these phrasal verbs are as follows.

called up means to make a phone call.

called on means to call for an opinion of answer.

called back means to return a call.
 
called off means to cancel.
 
The sentence is giving a sense that the marriage could not be completed or was cancelled due to some reasons. So, the correct phrasal verb which makes sense in the given sentence is “called off”.

The replied sentence is a statement that indicates something superficial, not a fact, therefore, ‘were’, is used with the singular noun because ‘this problem’ is the singular subject of the object clause in the subjunctive mood and in subjunctive mood plural verb "were" is used with everything. Hence option B is correct.

The word ‘memorable’, which means worth remembering or easily remembered, especially because of being special or unusual.So the option B is correct answer. 

Momentous:of great importance or significance, especially in having a bearing on future events 

Momentary:lasting for a very short time; brief. 

Immortal:living forever; never dying or decaying.

The word ‘implementation’ means the process of putting a decision or plan into effect; execution. So the option D is the correct answer. 

Accomplishment:something that has been achieved successfully. 

Initiation:the action of admitting someone into a secret or obscure society or group, typically with a ritual 

Resolution: a firm decision to do or not to do something

The Statement ‘May you live long’ is an Optative sentences,which express wishes. So the option B is correct answer..

When something is left in between more than 2 things or persons, ‘among’ is used. There are a number of wolves in the sentence hence the correct answer is option D.

If is used for introducing a conditional clause. 

Once means as soon as; when. 

Since is used in the intervening period between (the time mentioned) and the time under consideration, typically the present. 

Because is the conjunction used for the reason that; since. 

The sentence before the blank states that ‘key function’ is the main reason for continuation of ‘function’ and the reason behind this statement is stated in later part of the

sentence. Hence, option A is the correct answer.

The word that fits here is the noun 'mercy' and not the adjective 'merciful.' Since it is an abstract noun no article is needed before the word. Thus option A is the correct answer.