I forget the exact time ________ they reached the South Pole[ ]

The weather in summer in Beijing is cooler than _____ in Shanghai.

With the word“PM2．5"_____appearing in media reports，people pay greaterattention to it and seek health tips for smoggy days．

Flu is a very ______ infectious disease. Fever, headaches, coughing and fatigue are some of its ______ symptoms.

Just hang the towel ______ the back of the chair so that it will dry soon