• The sentence implies that the subjects did not give up the expedition even though they found themselves in an insecure situation.

• 'Precarious' meaning 'not securely held or in position; dangerously likely to fall or collapse' is the apt fit for the blank.

The meanings of the other words are:

• Pleasant = giving a sense of happy satisfaction or enjoyment.

• Permissive = allowing or characterized by great or excessive freedom of behaviour.

• Plausible = (of an argument or statement) seeming reasonable or probable.

Hence, option A is the correct answer.

The sentence is in the present perfect tense which means the action is completed or not completed so far. Thus, "never" and "then" are not correct contextually.
Now, we use "still" in an affirmative sense, and "yet" in a negative sense.
For example:
I still remember our first meeting.
I have not been successful yet.
This sentence is obviously a negative sentence. Thus, "yet" is appropriate to fill in the blank.

The most apt noun to be filled here is 'pattern' as it is a repeated decorative design. Hence, option D is the correct answer.

• Examined = to look at or consider a person or thing carefully and in detail in order to discover something about them.

• Pursued = to follow someone or something, usually to try to catch him, her, or it.

• Provided = to give someone something that they need.

• Observed = to watch carefully the way something happens or the way someone does something, especially in order to learn more about it.

• Here, we want a verb that mentions the careful watch on something.

• Thus, 'observed' is the most suited one.

• Dilemma = a situation in which a difficult choice has to be made between two or more alternatives, especially ones that are equally undesirable
• Proposal = a plan or suggestion, especially a formal or written one, put forward for consideration by others
• Inferiority = the condition of being lower in status or quality than another or others
• Thought = an idea or opinion produced by thinking, or occurring suddenly in the mind

• The word "whether" refers to expressing a doubt or choice between alternatives.

• Among the given options "thought" does not refer to the doubt properly.

• "Proposal" and "inferiority" is out of context of the sentence.

• "Dilemma", on the other hand fit the context well and makes the sentence meaningful.

• The given blank needs to be filled with a question tag.

• We use the same auxiliary verb in the tag as in the main sentence.

• Also, if the sentence is of a positive tone, we change it to negative in the question tag.

• In the given sentence, the modal verb, "can" has been used which will remain the same in the question tag.

• However, the question tag will be positive as the main sentence is a negative one (use of 'hardly').

• We will use the pronoun 'she' in the question tag. 

• Thus, 'can she' is the most suited one.

• Handsome= physically attractive in a traditional, male way
• Eloquent= giving a clear, strong message
• Convincing= able to make you believe that something is true or right
• Random= happening, done, or chosen by chance rather than according to a plan

• A speech cannot be handsome.

• If the speech is a random one, it cannot be compelling as compelling means believable or able to be accepted as true.

• Convincing and compelling are synonymous words and we know by using "not only...but also" we refer to the additional different feature/ information.

• For example: He is not only rich but also handsome.

• Thus, "Convincing" is also not appropriate.

• Thus "Eloquent" seems to be the appropriate fit in the given blank grammatically and contextually.

• Genetic = belonging or relating to genes received by each animal or plant from its parents.

• Exclusive = limited to only one person or group of people.

• Geriatric = for or relating to old people.

• Puerile = behaving in a silly way, not like an adult.

• The noun 'medicine' is written after the blank, so we need an adjective that is being modified by the noun.

• As the subject is talking about his/her grandfather, 'geriatric' will be the most suited one.