.
From Mum’s love, patience and understanding, I have learned what a huge responsibility ___ is to raise a child.
| A．it | B．that | C．this | D．one |
As the years passed, many occasions—birthdays, awards, graduations—________ with Dad’s flowers.
| A．are marked | B．were marked | C．have marked | D．had marked |
As the twentieth century, come to a close, the raw. materials for a great national literature were at hand, waiting_______.
| A．to use | B．to be used | C．to have used | D．to be using |
With the help of high technology, more and more new substances____in the past years.
| A．discovered | B．have discovered | C．had been discovered | D．have been discovered |
—You speak very good French! 
—Thanks. I __________ French in Sichuan University for four years.
| A．studied | B．study | C．was studying | D．had studied |
—Why don’t we choose that road to save time? 
—The bridge to it __________.
| A．has repaired | B．is repaired |
C．is being repaired | D．will be repaired |