**Core Concept**: Present simple tense for general truths. **Analysis**: The sentence describes a habitual fact about scientific work, requiring the present simple tense ('focuses'). Past (A) or future (C) tenses contradict the context. 'Has focused' (D) implies an ongoing action, which is less precise. **Key Hint**: Use present tense for universal statements. **Error Analysis**: A/C/D. Tense mismatch with general statements.