Correct the sentence as the underlined point-
Five years ago, on this date, I am sitting in a small Japanese car, driving across Poland towards Berlin.
a)Was sitting
b)Sat
c)Have been sitting
d)No improvement

Hint: Read the given sentence and understand what it means. Point out the tense of the sentence and the tense of the underlined word which needs to be replaced. Go through the options and choose the one which agrees with the tense of the sentence.

Complete answer: The given sentence says that ‘five years ago', which means that the sentence is in the past tense. Tense is a category that expresses time reference. Tenses are usually manifested by the use of specific forms of verbs, particularly in their conjugation patterns. The main tenses found in many languages include the past, present, and future.
Option ‘a’ is the correct option because ‘was’ is a helping verb for the past tense. It is the correct form of the verb which will correct the given sentence.
Option ‘b’ is an incorrect option because a helping verb or an auxiliary verb is necessary for the given sentence, to replace ‘am’ of the underlined part.
Option ‘c’ is also an incorrect part because ‘have been' is used with past perfect tense, which is not required here.
Option ‘d’ is an incorrect option as an improvement is being made.
Hence, option ‘a’ is the correct option.

Note: The main rule is that for every verb in English there is only one form of it in the past tense. This is totally different from other languages such as Spanish, French, Italian etc. Where you change the verb ending for every subject. For example, The past tense of the verb want is wanted.