Explanation:
The correct answer is option 'D', which is "images".

HTML Object Tag:
The HTML object tag is used to embed multimedia (such as audio, video, Java applets, etc.) into an HTML document. It allows you to include external content or media within your web page.

Embedding Multimedia:
The object tag is primarily used to embed multimedia content like audio, video, or Java applets. It provides a way to include external files or media directly into an HTML document.

Options:
Let's analyze each option to understand why 'images' is the correct answer:

a) Audio:
The object tag can be used to embed audio files into an HTML document. You can specify the source of the audio file using the 'data' attribute within the object tag. Therefore, the option 'audio' is incorrect.

b) Video:
Similar to audio, the object tag can also be used to embed video files into an HTML document. You can specify the source of the video file using the 'data' attribute within the object tag. Therefore, the option 'video' is incorrect.

c) Java Applets:
The object tag can be used to embed Java applets into an HTML document. Java applets are small programs written in the Java programming language that can be embedded and run within a web page. Therefore, the option 'Java applets' is incorrect.

d) Images:
The object tag is not suitable for embedding images into an HTML document. Instead, the 'img' tag is specifically designed for displaying images. The 'img' tag allows you to specify the source of the image using the 'src' attribute. Therefore, the option 'images' is correct.

Conclusion:
The object tag in HTML is used to embed multimedia content like audio, video, or Java applets. However, it is not suitable for embedding images. To embed images, the 'img' tag should be used.