为了交每月的租金，许多家庭不得不节省食物和其他必需品的支出。
Many families must skimp on their food and other necessities just to meet the monthly rent.
如果情况恶化，他们甚至不得不买回股票并将其推销给客户，因为他们必需在市场中有一席之地。
If conditions worsen, they may even have to buy back securities peddled to clients, as they are obliged to make markets in some of them.
不得不通过专用的扩展来添加这些必需的功能。
These necessary features have to be filled in with proprietary extensions.
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