Stand of China
The “technical hold” put by China on the proposal jointly moved by the U.S., the U.K. and France indicates its continued eagerness to shield Pakistan.

Pakistan had recently said the JeM leader, Azhar had been put under house arrest, even as US administration had renewed the proposal to designate Azhar terrorist, immediately after the Chinese veto in December.

Voting on terror issues at UNSC
When the UNSC meets as al-Qaeda, Taliban & IS Sanctions Committees, it works on the principle of ‘unanimity and anonymity’ — a single member’s opposition amounts to a veto, and the deliberations and the voting will remain secret.

India had last year opposed this practice which it called the “hidden veto”. Last year, China put the proposal on hold, first for six months, and then extended it for three months before finally blocking it altogether. Once it is ‘blocked,’ a new proposal can be moved.

Why India demands JeM and Azhar to be labeled as terrorists?  
The JeM is already a UN-designated terrorist organisation and China has so far refused to explain how it distinguishes the leader from the organisation. The question of Azhar — who was among the terrorists released by India following the hijacking of IC-814 in 1999 — came to the foreground last year after India held him responsible for the Pathankot attack.