Hint:Green schist are metamorphic rocks which can be used as a medium to make sculptures. The sculpture belongs to the Shunga period which decorated the great Stupa or relic mound in Madhya Pradesh. The flat planes and elegant detailing of ornaments suggest continuance of a tradition far earlier in wood.
Complete answer: The Bharhut sculpture was an early Indian sculpture of the Shunga period (mid second century BCE). It used green schist as a medium. The Bharhut style, despite being archaic and primitive in its conception, poses as a landmark of commencement of the tradition of Buddhist narrative relief. Similar scriptures are located across North India, suggesting that Bharahut was a center for this style. The stone railings are decorated with medallions and lunates; many are filled with lotus ornaments and some of them are centered by the head of a man or a woman. Many other railings depict Jataka Tales and the life events of Buddha. As in all Indian sculpture before the first century CE, the Buddha is represented by a symbol such as a wheel, empty throne, or umbrella, never in human form. Animals appearing in them are treated with sympathy and given human attributes. These sculptures stand as evidence of the art that people of the time were able to create as a remembrance of the time to come.
Hence, the correct answer is option (C).
Note:Mathura sculptures consisted of red sandstone while the Gandhara sculptures used bluish grey sandstones. The Mauryan sculptures were hard cut against the sandstone.