CSS Help: hide some DIVs on feeds' import page

Hi,

I am using the feeds (https://www.drupal.org/project/feeds) module to upload CSV for creating new nodes. The upload is done on the page http://www.mysite.com/import. On this page there are two dropdown options, i.e. Delimiter and File Encoding, as shown in following image:

Image: The DIV elements to be hidden

Since I want the uploading people use just the default option, I want to hide the dropdown options. By inspecting elements of the page, I see following HTML (see attached image 2).

Image: HTML of the import page

I an thinking using the CSS display property to hide these elements. For example,

.form-item-feedscsvparser-delimiter {
	display: none;
}

But no luck to hide the element.

Anyone can help me to solve the problem? Thank you very much!