English grammar error-spotting (choice of object phrase with ‘‘harmful’’ and welfare wording): Read the sentence segments and locate the error; select ‘‘No error’’ only if everything is correct. Consider precise idiom in object of ‘‘harmful’’: ‘‘Happily, zoos were / unwilling to cooperate / in a scheme that was potentially harmful to animal welfare / No error.’

Given data

• C: ‘‘in a scheme that was potentially harmful to animal welfare’’

Concept / Approach
In formal exam style, it is more idiomatic to make living beings the object of harm: ‘‘harmful to animals’’ or ‘‘harmful to the welfare of animals’’. The abstract compound ‘‘animal welfare’’ is typically used as a field/sector noun (e.g., ‘‘animal-welfare policy’’) rather than as the direct patient of ‘‘harmful to’’ in this structure.

Step-by-step correction reasoning
Replace C with a concrete object: ‘‘… harmful to animals’’ / ‘‘… harmful to the welfare of animals’’.

Corrected version
‘‘Happily, zoos were unwilling to cooperate in a scheme that was potentially harmful to the welfare of animals.’’

Common pitfalls

• Choosing overly abstract objects where a concrete patient is expected after ‘‘harmful to …’’

Final Answer
in a scheme that was potentially harmful to animal welfare