Question

高二英语的一个填空问题 ！！谢谢

Probiotic (益生菌) yoghurt and yoghurt drinks may not be as healthy as they are claimed to be. The European Food Safety Authority (FESA) has found that there is not enough evidence that these products have a positive effect on the immune system and digestive health.
The producers of these products have been claiming that these foods could help relieve digestive irregularity and impr ove the immune system. They have complained 【about】 the FESA standards, “Those must be the most strict standards, aren’t they?” However, their complaints don’t help consumers, who simply want to know whether probiotic food products, which range from yoghurts and yoghurt drinks to dietary supplements, are likely to benefit their health.

为什么填about 为什么不能是to？谢谢！

Answer 1

complian about 是 抱怨 的意思，complian to 是 “向...抱怨”，根据语义，应该用about。

Answer 2

about是抱怨、投诉什么事
to 是向谁抱怨、投诉

Answer 3

楼上两位都没说错啊