although / though / no matter +疑问词( 疑问词+ever) ::引导让步状语从句
1.Although/ Though he is young , he can help do a lot of housework
---Young as / though he is, he can help do a lot of housework
---Child as/though he is , he can help do a lot of housework
2.However difficult (=No matter how difficult ) it is , we may finish it in time.