THERE __________ A BIG INCREASE IN THE MARKET FOR MOBILE PHONES RE...

10. - KIEM TRA 1TIET SO 1 TRON 4 DE
KIEM TRA 1TIET SO 1 TRON 4 DE
10. There __________ a big increase in the market for mobile phones recently.A. has had B. was C. has been D. is