When exporting to SVG, if all lines appear with a thickness of 4, what could be the reason for this, and how can the lines be exported to the adjusted thickness?

a) The SVG export settings need to be adjusted to maintain line thickness.
b) The original document's line thickness settings are affecting the SVG export.
c) The SVG rendering software may be altering the line thickness.
d) The SVG format inherently renders all lines with a default thickness of 4.