【单选题】

The discovery of freezing has changed our eating habits more than any other related invention. Because many foods contain large amounts of water, they freeze solidly at or just below 32 degrees Fahrenheit. When we lower the temperature to well below the freezing point and prevent air from penetrating the food, we retard the natural process of decay that causes food to spoil. Freezing preserves the flavor and nutrients of food better than any other preservation method. When properly prepared and packed, foods and vegetables can be stored in the freezer for one year. 

Most vegetables and some fruits need blanching before they are frozen, and to avoid this step would be an expensive mistake. The result would be a product largely devoid of vitamins and minerals. Proper blanching curtails the enzyme action, which vegetables require during their growth and ripening but which continues after maturation and will lead to decay unless it is almost entirely stopped by blanching. This process is done in two ways, either by plunging vegetables in a large amount of rapidly boiling water for a few minutes or by steaming them. For steam blanching, it is important that timing begin when the water at the bottom of the pot is boiling. Different vegetables require different blanching times, and specified times for each vegetable must be observed. Under-blanching is like no blanching at all, and over-blanching, while stopping the enzyme action, will produce soggy, discolored vegetables. 
1.Why does the author mention 32 degrees Fahrenheit? 
A.To suggest the storage temperature for most foods 
B.To identify the freezing point of water 
C.To state the correct setting for a freezer 
D.To give the temperature for blanching 
2.Why does the author use the term expensive mistake in discussing blanching? 
A.To state that blanching is expensive but very effective 
B.To warn that not blanching will harm the food’s nutritional value 
C.To emphasize the importance of blanching only a few items at a time 
D.To show that many people waste food by blanching improperly