Final answer:
The correct answer is option a. False Dmitry II.
Step-by-step explanation:
The individual known as the 'Thief of Tushino' was False Dmitry II. After the death of False Dmitry I, who had impersonated the son of Ivan IV (Ivan the Terrible), False Dmitry II appeared in Tushino, a village near Moscow, and claimed he was the person who had previously impersonated Dmitry Ivanovich.
His pretension to the throne during the Time of Troubles created a period of instability and civil strife in Russia as he gathered a following and attempted to claim the tsardom.