Ileft for the airport. after i finish packing my bags.

Sentence fragment

Explanation:

A sentence fragment fails to be a sentence because it cannot stand by itself. It does not contain even one independent clause.

After I finished packing my bags is a sentence fragment because it is a subordinate, or dependent, clause. It cannot stand by itself. It is a subordinate clause fragment. You need to attach an independent clause to make it a sentence. For example, "I left  for the airport after I finished packing my bags." That would be a correct sentence.  

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

i would pick a. i think this is more of a personal question though.