问题补充：
It was the old worker came that we the experiment.
A. until; didn’t begin
B. not until; began
C. until; began
D. not until; didn’t begin
答案：
A. until; didn’t begin
B. not until; began
C. until; began
D. not until; didn’t begin
解析：本题句式结构为强调句型。强调until引导的时间状语从句,要把not放于until之前。
