Fill in the Blanks

Since is the correct conjunction here as it means 'counting from the time when'. When means 'at the time' and doesn't refer to continuity.

 (Since she was) stricken with grief...

 Is about to finish it indicates continuation in the present. Hence, the commencement will be indicated in present perfect continuous tense. 

 'Whenever' indicates a routine. 'Is' is indicative of present. To present routine in the present, verb in the simple present tense will be used.

Defer to means to accept something.

Answer will be 'to" as one condition 'leads to' another condition.

'Repent for' is the correct prepositional usage. It means 'to feel such regret or dissatisfaction over some past action, intention, etc.'

Some words like 'depart', 'separated', 'abstain', etc are always followed by preposition 'from'.

Case of multiple prepositional usage. 'Look at' means 'to observe or examine someone or something'. 'The indifference' is an abstract noun, and except proper personal nouns we use preposition 'with' for all nouns. We show indifference 'towards' somebody. Thus, option 4.

The sentence implies that we left the airport immediately after the flight took off. So, 'as soon as' is the correct conjunction here.

In case refers to an assumed condition (if it should happen that). Option 3 doesn't fit here as the preposition 'of' cannot be used here. 

Here, a reason for not attending the marriage has been given. So, 'as' is the correct conjunction.

Although is used to present an idea contrary to the expectation or norm, which is the case here. So, option 2 is the correct answer.

We need a word to refer to the time to connect two events at a point of time. So, option 4 is the correct answer.

Note the difference: If you spoke...we could... (present conditional) If you had spoken...we could have... (past conditional)