Which of the following words is closest in meaning to “Placid”?

Placid means calm and peaceful.

• Correct answer - calm: it has the same meaning as Placid.
• hard working: diligent - wrong, it does not mean the same as Placid.
• boring: dull - wrong, it does not mean the same as Placid.
• rough: not smooth - wrong, it does not mean the same as Placid.