Answer is E

This question can be rephrased as "In which decade was the debt with dark grey rectangular bars half of the debt in light grey rectangular bars?"

2000s is the only decade where the debt held by government accounts (dark grey bars) is ever closest to half of all federal debt (debt held by public / light grey bars)

Note: the debt held by the public (light grey bars) also includes the debt held by Federal Government Accounts (dark grey bars)