作者原文和翻译（不对之处请指出）：

In order to allow for the experimental observation of gravitational bound states, all interactions of the matter particles with other fields must be so small that their interference with the gravitational quantum phenomena can be neglected. The choice of neutrons seemed to us most favourable because (1)they are neutral, (2) they have a long lifetime, and (3) they are elementary particles with low mass. The reasons why these properties are advantageous will become more evident from the following explanations.（为了顾及引力的束缚态的实验观测，所有的物质粒子在其他场中的相互作用力必须小到它们对引力的量子现象的干扰能够被忽略。在这里中子看起来就成了我们最好的选择，因为：（1）他们是中性的。（2）他们是长寿命的。（3）他们是低质量的基本粒子。下面的我们将进一步证明为何这些特性是有利的因素。）

亲爱的网友，看完上面这一段话后，您认为：

1）作者是为了研究中子而选用了引力场。

2）作者是为了研究引力场而选用了中子。

请选择1）或2）

谢谢！