This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Q: The Kushan Empire expanded out of what is now Afghanistan into the northwest of the subcontinent under the leadership of their first emperor, Kujula Kadphises, about the middle of the 1st century CE. They came of an Indo-European language speaking Central Asian tribe called the Yuezhi, a branch of which was known as the Kushans. By the time of his grandson, Kanishka, they had conquered most of northern India, at least as far as Saketa and Pataliputra, in the middle Ganges Valley, and probably as far as the Bay of Bengal.
A:
From what area did the Kushan Empire come?