None of the above. The options offered do not gell with what is known so far.
The facts we (think we) know are;
i) Team (a) had a block of flats under surveillance and saw a dark skinned man leave the building
ii) Team (a) whilst realising the man did not match the pics of any of the bombers decided he was worth tailing anyway in case he led to something bigger and so assigned a few of their number to the task.
iii) Some members of team (a) followed the 'suspect' to a bus stop where he took a 15 min ride to Stockwell tube station.
iv) At the station team (a) handed over control to team (b) SO19 specialist marksmen.
v) the 'suspect' entered the station and team (b) made a decision to not allow him to get on a train.
vi) The suspect got on the train and was shot dead by the members of team (b)
The circumstances of what occurred in the station are clouded in controversy with wildly differing accounts and so there are
no reliable facts available other than that he was shot 8 times..
However from the information above I believe it is safe to assume that team (a) whilst thinking the 'suspect' was worthy of following did not view him as a primary terrorist candidate because if they did they were grossly incompetent in allowing him to board a bus.
When control passed to team (b) it appears the level of 'suspicion' was not clearly communicated and so team (b) it seems elevated his standing from the mild suspect status that team (a) had afforded him to a clear and present danger.
From that point how team (b) reacted is the subject of conjecture as the police, apart from a few unsubstantiated, unattributed leaks to the media have been deafeningly silent on the details.
However what we do know is that if he had been a suicide bomber several people would have been dead as the police allowed him to spend 26 minutes between leaving his house and shooting him during which time he not only spent 15 mins on a bus but also managed to enter an underground train.
From this I do not see how it is possible to conclude other than that the police were incompetent in the way they managed this whole episode.
Edit: Link added -
http://www.timesonline.co.uk/article/0,,22989-1707480,00.html