The noise-killing system is not yet popular mainly because ______.
A: it is still being tried out
B: drivers still have their doubts
C: it increases the cost of car production
D: carmakers are not sure if it is necessary
A: it is still being tried out
B: drivers still have their doubts
C: it increases the cost of car production
D: carmakers are not sure if it is necessary
举一反三
- This is a very popular book in the U.S., but it died have a history of being banned in Europe, and it was still ＿ in many countries.
- Have you not been on the London Eye? A: already B: yet C: still
- It is true that there are still abundant reserves of metals which have not yet been______, but it is necessary to take steps to ensure that alternative materials are substituted whenever possible. A: utilized B: mobilized C: acquired D: cultivated
- The underground connection ___ when I moved into the house. A: is still being built B: was still being built C: was still building
- —Have you read the book yet— Yes, I have （）read it. A: always B: just C: still