Explanation
False: You cannot create a new clipping boundary without removing the existing clipping boundary. If you want to change the clipping boundary, you have to select the PDF underlay, right-click and choose Remove Clipping Boundary first, and then use the Clip PDF command again with a different option12.
True: To access the Underlay Layers dialog box, you have to select a PDF underlay, right-click and choose PDF Layers2. In the Underlay Layers dialog box, you can click the light bulb icon for the layer name that you want to turn on or off2.
True: To use the Align command, you have to select a polyline, right-click and choose Align3. Then you have to specify two source points on the polyline and two destination points on the PDF underlay that correspond to each other3. You can also specify a third pair of points if needed3. Finally, you have to press Enter twice to confirm the alignment3. The statement "You can use the grips on the polyline to align to the edges and corners of the PDF underlay" is true. When you place a rectangular polyline over a PDF underlay and use it as a clipping boundary, the polyline's grips can be used to adjust its size and position so that it aligns with the edges and corners of the underlay.
By hovering the cursor over a grip, you can see its tooltip display the name of the grip and its function. If you then click and drag the grip, you can move it along its corresponding axis to resize the boundary. This allows you to adjust the clipping boundary to fit exactly over the content you want to display.

associative dimensions adjust to changes in the geometric objects they measure. Dimension associativity defines the relationship between geometric objects and the dimensions that give their distance and angles.
Based on 2 and 3, dimensions in a layout may be associated to objects in model space when the DIMASSOC system variable is set to 2.

Explanation
From the Delta option of the Lengthen command, enter 50 units and then select the right end of the line. This way, you can increase the length of the line by 50 units from its current endpoint without changing its direction or position2
https://www.learnvern.com/autocad-tutorial-in-hindi/how-to-use-lengthen-command

* Understanding Multileader Components:
* Multileader annotations consist of a leader line and a block (circle in this case).
* The display of these components is influenced by their layer and color settings.
* Layer and Color Settings:
* The leader portion appears blue because it is on the LEADERS layer which is set to blue.
* The circle block appears green because its content is on Layer 0 and set to ByBlock. This means the block takes on the properties of the layer it is inserted on unless overridden.
* Combination of Color Settings:
* Option D: ByLayer for the leader and Green for the block results in the leader being blue (from the LEADERS layer) and the block being green (explicitly set to green).
* Option B: ByLayer for both the leader and block means the leader is blue (from the LEADERS
* layer) and the block inherits the green color set in its definition.
* Conclusion:
* The two correct combinations to achieve the described color settings are ByLayer Green and ByLayer ByLayer.
References:
* AutoCAD Help Documentation on Multileaders.
* AutoCAD User Guide on Layer and Color Management.