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Animal signals, such as the complex songs of birds, tend to be costly. A bird, by singing, may forfeit time that could otherwise be spent on other important behaviors such as foraging or resting. Singing may also advertise an individual's location to rivals or predators and impair the ability to detect their approach. Although these types of cost may be important, discussions of the cost of singing have generally focused on energy costs.
It can be inferred from the passage that compared with other costs of singing, which of the following is true of the energy costs of singing? （多选题）
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A.They are the single greatest cost to an individual bird.
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B.They have generally received more attention from scientists.
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C.They vary less from one bird species to another.
B显示答案
