"has been" as a auxiliary verb
 

"One need to explain and emphasize the nature and extent of US military aid to Pakistan's military to highlight how critical this [[SIZE="5"]B]has been[/B[/SIZE]] to Pakistan's army. here has been makes what sense? is it mean k ye imdad pakistan ke leye kitne zarore reh chuke hai??

i am so confused pertaining to use of Has been. have been and had been as auxiliary verbs.
plz guide

Yes.

[B]Present Perfect Continuous Tense[/B]
''Has been critical to Pak Army'' means it indicates an activity or state that extends over a period of time that began in the past and includes the present.

[B]Has been[/B] for singular noun like he, she, it etc.
[B]Have been [/B]for I, we, they etc.

[B]Past Perfect Continuous Tense[/B]
To indicate any activity which was continuous or it was still going on at the point or period of past time.

[B]Had been[/B] for all subjects.