The core concept tested here is the understanding of the function of past participle phrases in sentences. The correct answer is B, as the past participle phrases 'anchored in the deeper layers of the earth' and 'needed to resolve the question' provide additional information about the 'measuring instruments'. Option A is incorrect because the past participle phrases do not modify the subject 'Hot spots'. Option C is incorrect because the phrases do not indicate time. Option D is incorrect because the phrases do not show the result of an action.