Since each slide layout has predefined placeholders, the original properties of a placeholder can be restored at any time. To do so, select the placeholder.
Then choose the ribbon command Design | group Placeholders | Reset placeholder 
.
Tip: Alternatively, you will also find the command in the context menu or on the contextual ribbon tab Object, which appears as a tab on the far right.
Then select one of the following options:
▪Reset object properties: This option resets the object properties of the placeholder to the original state (except text formatting, size and position).
▪Reset text properties: This option resets all character and paragraph formatting for the placeholder.
▪Reset size and position: This option resets the size and the position of the placeholder.
▪Reset all properties: This option resets all three of the aforementioned properties (object properties, text properties, size and position). For more information, see also Resetting slides.