21.   The field is becoming both more specific and more competitive.

22.   The field slowly becomes one big, slushy mess of tomato sauce.

23.   The N.D. field is becoming mainstream.

24.   The more crowded Republican field was becoming more raucous, the more intimate Democratic contest growing a bit testier.

25.   The two fields have become increasingly intimate.

26.   When the rains subsided, the rice and corn fields became a feast for insects.

27.   With their withdrawals, the Republican field is becoming clearer.

28.   By last October, its blooming fields had become the front line of the war between the U.S.-backed northern alliance and the Taliban.

29.   However, the field became especially crowded about five years ago, when drug companies started to research chemicals that might stop the process as possible cancer treatments.

30.   The Caspian fields could become a huge source of oil and gas on world markets.