ARussia is against the sanctions imposed by the USA but China does not want to show that it is going against US ban.
BRussia and China both support the sanctions imposed by USA on Iran regarding its trade relations with other countries.
CUS and China both support Russia but Russia is in favour of Iran on the issue of trade sanctions by the USA.
DRussia and China support the trade relations of Iran with other countries and they are completely against any kind of sanction by USA.