The concept of time zones was invented to solve a pressing issue (18) ________ in the 19th century

18/40

The concept of time zones was invented to solve a pressing issue (18) ________ in the 19th century.

the burgeoning railroad industry was faced

the burgeoning railroad industry had faced

was faced by the burgeoning railroad industry

faced by the burgeoning railroad industry

Giải thích

D: cấu trúc mệnh đề quan hệ rút gọn bổ nghĩa cho danh từ ngay trước nó ‘a pressing issue’, ở dạng quá khứ phân từ V3/ V-ed khi mang nghĩa bị động.