By occupying the Earth-Moon L2 Lagrange point, where the gravitational forces from Earth and the Moon are in equilibrium, the THEMIS satellite—which studies Earth’s magnetosphere—maintains a constant orbital position relative to the Moon. The orbital stability of objects positioned at a Lagrange point is not _____ spacecraft occupying the Earth-Moon L2 Lagrange point still need to make occasional adjustments, using small amounts of fuel to fine-tune their positions.
Which choice completes the text so that it conforms to the conventions of Standard English?
Explanation
Context: "The orbital stability of objects positioned at a Lagrange point is not perfect, though; spacecraft occupying the Earth-Moon L2 Lagrange point still need to make occasional adjustments..." "Though" connects two independent clauses — comma before, semicolon after.
Answer: C) perfect, though;
Why? Pattern: comma before "though" + semicolon after it. [clause], though; [clause].
Traps:
- A) "perfect, though," → comma after "though" = comma splice
- B) "perfect, though" → without semicolon, creates comma splice
- D) "perfect; though" → semicolon before "though" = reversed