This is probably not done by India. China is implying they have some ideas of possible groups who did this which means they have some information on it by now. If it is India, China would have mentioned it and presented some evidence on it or at least claim this. It is something that China would love to do and focus attention on how India is using terrorists. It has not done that yet but already has suggested it knows at least some information on identity. So if it is India, China would have said already and condemn and accuse them.
Imagine if Chinese financed terrorist attacked American engineers working in India and USA has some evidence to suggest it is Chinese terrorists or funded by China? They would be talking about it for a few years.
Chinese are not like Indians. They will wait and announce the culprits after throw investigation. It is only Indians who have superpower to find the culprits after few minutes of any incident.