Up to now, no one has come up with a（n）       explanation of why dinosaurs died out, and it remains a mystery．

 Women at that time were ________ the right to vote because they were not treated equally as men.

 The supermarket _______ that the customer should pay for the damage.

Since your English is poor, why not ________ an English club to improve it?

While I was in the foreign country, my younger brother always ____ me of what was happening in big cities in time.