过去几天里，这座城市交通拥堵的情况越来越严重。

There has been a steady ___buildup of traffic congestion in the city over the past few days.

多年的灰尘堆积使这台老机器难以运转。

The ___buildup of dust over the years made the old machine hard to operate.

这部电影的前半部分都是为最后的高潮戏做铺垫。

The first half of the movie is all about the ___buildups leading to the final climax.