Title: Cotton.
Question: What did a 2012 study suggest  was halved by the use of GM plants?

Title: Hydrogen.
Question: What form can you find hydrogen is on Earth?

Title: Nanjing.
Question: On what days did Nanjing have to issue a Red Alert because of the severe air pollution?

Title: The Blitz.
Question:
What mechanism cause the bombs to be released?