Mark the letter A, B, C, or D to indicate the underlined part that needs correction in each of the following sentences.
1.Before steel and concrete was introduced as building materials, carpenters had played the major role in construction
2.Industrial wastes that man discharges them into the sea have a deleterious effect on marine life
3.The company is introducing a fire-prevention system that activated by any small increase in temperature.
Mark the letter A, B, C, or D to indicate the underlined part that needs correction in each of the following sentences.
1.was => were
2.discharges => discharge (bỏ "s") ; have => has
3. activated => is activated
1. Sai "was introduced"
Sửa: were introduced
2. Bỏ "them"
3. Sai "that activated"
Sửa: that is activated
