Solution
Option 3: Common Houseplants May Purify Your Home is the correct answer.
A good title captures the main idea of a passage. The passage is about how everyday houseplants can help clean the air inside your home. Let's see why the other options don't work:
Option 1: "Research in the New Millennium" is too broad — it could be about any kind of research and doesn't mention plants or homes.
Option 2: "Home Dangers" only covers half the story. The passage isn't just about dangers at home — it's about how plants can help solve those dangers.
Option 4: "Plant More Trees" is about outdoor trees, but the passage focuses on indoor houseplants — not the same thing!
Option 3 fits perfectly because it tells us what (common houseplants), where (your home), and what they do (purify, which means "make clean"). A good title always summarizes the most important idea of a passage, and this one does exactly that!