Which two statements are true about Placeholder & Placeholder definitions in Oracle Site Studio?

Anwser
B and C
http://docs.oracle.com/cd/E10316_01/SiteStudio/10gr4/WebHelp-Designer/c02_websites014.htm#CJAGACGJ

A
What the contribution region identified by the placeholder contains, and how it looks on the site, is defined using region templates and region definitions (see Region Templates and Region Definitions). A page template may contain multiple placeholders, each of which representing a contribution region on the page. There are no files associated with placeholders; that is, there are no “placeholder files” on the content server. Figure shows a representation of a web page that contains one placeholder, marked with a dotted line (with sample content in place).

B
“Placeholder definitions specify what content can go in a contribution region (as marked by a placeholder tag) and how this content is displayed, as well the actions available to contributors. For example, a placeholder may be set up to allow contributors to update the metadata of content displayed in the contribution region, or they may be allowed to switch the content of contribution regions. (Please note that region definitions control what kind of content contributors can switch to.)”

C
“Placeholder definitions also specify what region definitions, region templates, and subtemplates are available for the associated placeholder (that is, contribution region) on the web page. Take, for example, the placeholder definition shown in Figure, which allows three region definitions: REGION_DEFINITION_1, REGION_DEFINITION_2, and REGION_DEFINITION_3.”

Regards
Aurélio