Selective breeding on food crops may create stronger, and more healthy crops. The idea is to find your best crops, and breed them with other crops sharing the traits you want.
Answer:
D. build them up and breaks them down
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Mediastinal shift occurs in Tension pneumothorax. A tension pneumothorax makes the lung to collapse and the heart, the trachea and the great vessels, to shift toward the unaffected side of the chest. When air moves out from a laceration in the lung and goes in the pleural space or infiltrate the pleural space over a wound in the chest wall the shift happens.
The fish are eaten by ducks. Ducks cannot really swallow preys that are too big for their throats. They usually swallow organisms that are a lot smaller than fishes. because they do not have the capacity to bite and chew their preys.