We need a head of lettuce, a bunch of carrots, and a bag of Onions.

我们要一棵生菜，一把胡萝卜和一袋洋葱。

I'll take a pineapple, a head of cauliflower, two bunches of celery, and a head of lettuce.

我要一个菠萝，一个菜花，两把芹菜，一头莴苣。

Washed and bagged greens can be a time-saver, but they can cost three times as much as buying the same amount of a head of lettuce.

购买洗净、包装好的绿色蔬菜可能会节省时间，但这可能比购买等量的一棵莴苣要贵三倍。

It all seems so simple: Hit the "place order" button online and get a head of lettuce, a dozen eggs, or a gallon of milk delivered to your doorstep within 24 hours.

一切似乎如此简单：在网上点击“提交订单”的按钮，一棵莴笋、一打鸡蛋或是一加仑牛奶就会在24小时内送货上门了。

If it costs 10 percent more to produce a US-grown head of lettuce, for example, lettuce imports are likely to increase by 3 percent, according to Dr. Kagan's research.

例如，根据kagan博士的研究，如果美国国内莴苣成本增加百分之10，进口莴苣的价格有可能增长百分之3。