Follow Michiko Kakutani on Twitter: @michikokakutani
After the attacks, bin Laden and al-Zawahiri released additional video tapes and audio tapes, some of which repeated those reasons for the attacks. Two particularly important publications were bin Laden's 2002 "Letter to America",  and a 2004 video tape by bin Laden. 
I would like to know if I should mention number of words at the end of my essay for both Task 1 and Task 2.
On 24 September, FSB director Nikolai Patrushev announced that the exercise was carried out to test responses after the earlier blasts.  The Ryazan FSB "reacted with fury" and issued a statement saying:  "This announcement came as a surprise to us and appeared at the moment when the ...FSB had identified the places of residence in Ryazan of those involved in planting the explosive device and was prepared to detain them." FSB also issued a public apology about the incident.  In a live show on NTV Evgeniy Savostoyanov former FSB director in Moscow categorically denied that any such exercise could be performed on residential buildings with inhabitants inside and without notifying local authorities.