Answer:
D). 'Mountains' doesn't need to be capitalized.
Step-by-step explanation:
The given sentence is error-free except for point D where it incorrectly capitalizes the common noun 'mountains'. As per the rules of 'capitalization', a noun need not be capitalized unless it is a proper noun or adjective derived from that and due to disregarding this rule, D part of sentence locates an error. Therefore, this makes us conclude with an assured response that suggests that the first letter of 'mountains' should not have been written in upper case.