The 80000 objects collected by Sir Hans Sloane_______ the corecollection of the British Museum opened in 1759.（2022新高考考试I）
官方答案是formed，这里为何不可以用had formed？
form在此为静态系词，表示一种状况的存在，而不是表示动作的发生。这个句子表示的是过去的状况，所以用一般过去时。以下为牛津词典对form这个语义的解释和例句：
have function/role
linking verb + noun： to be something; to have a particular function or pattern
The castle forms the focal point of the city.
The survey formed part of a larger programme of research.
These drawings will form the basis of the exhibition.
This family forms the core of the film.
The trees form a natural protection from the sun's rays.
