The correct answer is option 1: Liquid nitrogen.

Storage of biological tissues such as blood, organs, and semen requires low temperatures to preserve their viability. Liquid nitrogen is commonly used for this purpose due to its extremely low temperature of -196 degrees Celsius (-321 degrees Fahrenheit).

Option 2: Solid carbon dioxide, also known as dry ice, is also capable of reaching very low temperatures, but it is not commonly used for long-term storage of biological tissues. It is more commonly used for short-term shipping and transport of perishable goods.

Option 3: Liquid air is not typically used for the storage of biological tissues. It is a mixture of the components of air (oxygen, nitrogen, argon, etc.) and its temperature is typically higher than that of liquid nitrogen.

Option 4: Helium is a gas and does not have the ability to achieve low temperatures required for the storage of biological tissues.

In summary, liquid nitrogen is the preferred choice for storing biological tissues due to its extremely low temperature and its ability to maintain the viability of these tissues over extended periods of time.