Question 1 --> The answer is A.

A. the nutritional and energy demands of egg production
The passage mentions the debate among biologists regarding the costliness of egg production, with some suggesting that it is energetically or nutritionally demanding. Lack's theory, as mentioned in the passage, focuses on clutch size evolving in relation to the number of young that parents can successfully rear. Therefore, the nutritional and energy demands of egg production are central to this perspective.
B. the number of young that the parents can rear successfully
This is actually the view presented by Lack, as mentioned in the passage. Lack suggested that clutch size evolved in relation to the number of young that parents can successfully rear. Therefore, this aligns with the proposed perspective in the passage, but it does not represent the viewpoint that egg production is biologically highly costly.
C. reproductive limitations operating during chick rearing
This option mentions limitations during chick rearing, which is part of Lack's later recognition. However, the passage suggests that Lack's initial theory was focused on clutch size evolving in relation to the number of young parents could successfully rear, not on reproductive limitations during chick rearing.
D. the availability of food for newly hatched chicks
This option refers to the availability of food for newly hatched chicks, which is not the primary focus of the debate mentioned in the passage. Lack's later recognition discusses factors affecting clutch size in precocial species, but the focus of the initial debate is on whether egg production is biologically highly costly.
E. the differences between altricial and precocial species
The passage does discuss the differences between altricial and precocial species but in the context of factors affecting clutch size. The primary debate, however, is about whether egg production is biologically highly costly. The differences between altricial and precocial species are brought up later in relation to clutch size but are not directly addressing the costliness of egg production.

Question 2 --> The answers are A and C.

A. In altricial species, clutch size is determined primarily by factors operating after eggs are laid.
This statement aligns with Lack's initial theory, as mentioned in the passage. Lack suggested that clutch size had evolved in relation to the number of young that parents could successfully rear, which involves factors operating after eggs are laid.
B. In precocial species, clutch size is determined primarily by factors operating after eggs are laid.
This statement may not hold for precocial species where the young feed themselves shortly after hatching. In such cases, post-natal factors might have less influence on clutch size.
C. In many bird species, clutch size generally remains well below the potential limit of egg production.
This statement is consistent with Lack's perspective. The passage indicates that Lack suggested clutch size had evolved in relation to the number of young that parents could successfully rear, implying that clutch size remains below the potential limit.