(a) The graph for an immobile object at \( x = 3 \, \text{m} \):
\[
\boxed{\text{Horizontal line at } x = 3 \, \text{m}}
\]
(b) The graph for an object starting from the origin with a constant positive velocity \( v_x > 0 \):
\[
\boxed{\text{Straight line with positive slope passing through the origin}}
\]
(c) The graph for an object starting from \( x < 0 \) with a positive velocity \( v_x > 0 \) and a positive acceleration \( a_x > 0 \):
\[
\boxed{\text{Upward curving line starting from a negative position}}
\]