In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Q: Question: How long did the period which Haig Fras was dated last? Passage:The Haig Fras outcrop consists mainly of granite, forming a WSW-ENE trending elongate intrusion. The granite outcrop is surrounded by an area of Devonian-Carboniferous sedimentary rocks. Evidence from gravity data suggests that the extent of the intrusion is greater than the observed outcrop, based on its association with a linear negative gravity anomaly. It is dated at 277 Ma, Early Permian in age, within the range of intrusion ages for the granites that make up the Cornubian batholith. Although the two intrusions have the same trend and are of similar age, they are not thought to be related. In detail, three separate outcrops have been identified using a combination of radiometric data and seabed sampling. The granite is fine to medium-grained, unlike the megacrystic granite typical of the Cornubian batholith intrusions, although this may be due to the low level of sampling available. A foliated granite is locally developed as a marginal facies.
 Links: a. Radiometric dating b. Sedimentary rock c. Cisuralian d. Cisuralian
A: 
c