Answer:
Hard rock mining is a technique used to excavate hard minerals...
Explanation
Hard rock mining refers to various underground mining techniques used to excavate hard minerals, usually those containing metals such as ore containing gold, silver, iron, copper, zinc, nickel, tin and lead, but also involves using the same techniques for excavating ores of gems such as diamonds or rubies.
The problem of the sentence in a research paper is reflected in option A) Dialogue is not appropriate for making assertions in a research paper. Dialogues can be used in narrative essays but are inappropriate for research essays.
In a research paper you are expected to find an analysis and interpretation of data collected in a given topic. Therefore, the author of a research paper analyses and interprets the research findings based in objective data.