There is no error in the sentence. The combination "one of the + noun (plural)+ who" is always followed by plural verb. For example:

Sunil is one of the students who have got scholarships.

• The error is related to 'being'.

• We use "being" as an adverbial participle clause to express reason or cause as an alternative to a because/since/as clause.

• Here the use of "being" at the beginning of the sentence imparts incorrect meaning to the sentence.

• We need to add a dummy subject "it" before "being" to give the sentence the required meaning (it is a sunny day, therefore he decided to skip work and stay at home).

• In order to make the sentence correct, add pronoun 'it' before 'being'.

• The error is in the usage of noun 'informations'.

• 'Information' is an uncountable noun and it is used in the singular as well as plural form without adding "s" in it.
  
  • E.g. :- Do you have any information about train times?

• Thus, replace 'informations' with 'information' to make the sentence grammatically correct.
  
  

The sentence is grammatically incorrect and option A has the grammatically incorrect part. The use of "since last Friday" indicates that the sentence is present perfect continuous. The correct auxiliary verb to use in the present perfect continuous is "has/ have been".

For example:
I have been studying for three hours.
He has been playing football since Morning.

Therefore using the verb "is" would be incorrect here and it needs to be replaced by the verb "has been".

Option A has the grammatically incorrect part. The error is in the use of the preposition "off".

• The phrase "pull yourself together" means to begin to live in a good and sensible way or to stop being confused, foolish, etc.
  
  e.g. Her life got much better when she stopped drinking and got herself together.
  
  
• The use of 'off' is incorrect here as it is a redundant word and needs to be omitted to make the sentence grammatically correct.

• Article “a” is used before words that start with a consonant and “an” before words that start with a vowel.

• But, when a word starts with a vowel but sounds like a consonant, it takes "a" before the word.

• For example: A university

• The word "unit" begins with a consonant sound "-yu" which means it must be preceded by article "a".

• Thus the article ‘an’ before the word ‘unit’ is incorrect.

• Replace "an" with "a" to make the sentence grammatically correct.

Option B has the grammatically incorrect part. The error is in the use of the word "back" after "returned".

• The verb "return" means to come back.
  
  
• As it already consists of the meaning of back, it is incorrect to use the word "back" with it. 
  
  
• Thus, remove the word "back" from the sentence.

• Here, the error is in the usage of the auxiliary verb 'were'.
  
  
• When we use correlative "neither…….nor", the verb agrees with the number and person of the nearest subject.
  
  
• The nearest subject to the verb is 'lion' which is singular in its form.
  
  
• Thus, replace 'were' with "was" to make the sentence grammatically sound.
  
  

• "Laid" is the past form of the verb 'lay' which means to put (something) down gently or carefully.
  
  e.g. She laid the blanket on the floor when I asked.
• "Lie" is a verb that commonly means “to be in or to assume a horizontal position”. 
  
  e.g. I felt sick, so I lay down.
  
  
• The correct verb here would be 'lie'.
  
  
• The sentence mentions two events and one action follows the other. 
  
  
• The action of lying should be the 1st in the sequence which would be followed by the other where somebody came to rescue him.
  
  
• Thus, we will use the past perfect tense for the action that happened first.