Trading and mining would be the most profitable, but you need knowledge and experience to be able to trade successfully.
And for the miners, the Antminer L3 by bitmain makes about $7 in revenue per day, while the Titan makes $40-60 a day.
Of course the Wolf V1 has the most hashing power, it makes $130 a day but it's much more expensive (over €6000), so your choice depends on your budget.

Bitcoin lending can be quite profitable, but only if you own relatively large quantities of btc and don't need them available for trading.
And completing tasks to earn btc only makes little money, but of course it's the least complex as well.