X. Rewrite the following sentences, using the provided word keep meaning as that of the root one.
33. I've never had to wait this long for a bus before.
=> This is……………………………………………
34. Remember to take note of what the tour guide said.
=> Remember to put……………………………………
35. It took us more than 3 hours to discover the inner Hanoi.
=> We spent……………………………………………
36. No other book is more popular than Dickens' "David Copperfield".
=> Dickens' "David Copperfield" is …………………………………
