A kiwi bird is ______. A: as heavy as four hens together B: as big as a hen C: as big as an egg

Generally, the supplemental amount of calcium in the feed of laying hens is ( ) A: 3.5-4.5% B: 1-2% C: 1.5-2.5% D: 2.5-3%

The writer is satisfied with the life in the countryside only because their hens can lay eggs for them and their bees can provide them with honey ...

操纵子学说的创立者是： A: Watson & Crick B: Nirenberg C: Krebs D: Jacob & Monod E: Hens Kebs & Kurt Henseleit

操纵子学说的创立者是： A: Watson & Crick B: Nirenberg C: Krebs D: Jacob & Monod E: Hens Kebs & Kurt Henseleit