True Statement about Tag

The following is an entry in JSTL's Core tags descriptor.
Select the true statements about this tag.

<tag>
<description>
Catches any Throwable that occurs in its body and optionally
exposes it.
</description>
<name>catch</name>
<tag-class>org.apache.taglibs.standard.tag.common.core.CatchTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>var</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>

Answers
1) This is an example of an empty tag.

2) The attribute "var" cannot use a JSP runtime expression.

3) The tag may have the attribute "var" supplied.

The correct answers are 2) and 3).

I didnt got it how the answer 3) is correct?

<rtexprvalue>false</rtexprvalue>

means that the tag can't take JSP runtime expression as its value which means that values which are present at runtime can't be used.

Thanks for replying.
How abt answer 3?

3) There's an tag attriubte called "var" which is not required. So The tag may have the attribute "var" supplied.

Thanks Verre Super Bar Tender for reply. But you can see in JSTL core descriptor, the tag attribute 'var' is already there present. SO how it can be supplied?. The thing which is already present how can again be supplied. There can be one reason for that the element <required> is false. That's why it says to be required but it doesnt makes much sense. what you think?

It means that when you use this tag you can either use (supply) the var attribute :
<c:catch var="bob"> ....
or not
<c:catch> ....

i got it, its pretty confusing,,, to understand to depth but thanks very much...