Strong root systems and long flexible stems allow plants to survive in the strong currents of which ecosystem? ponds rivers lakes the open ocean

I think the answer is River

Strong root system and long flexible stems allow plants to survive in strong currents of River Ecosystem

Explanation:

River is a body of moving water. River currents are quite strong to wash away and damage plants. To Avoid such Damage and washing away by the strong current the aquatic plants growing in river have strong root to anchor tightly to the river bed and flexible stem to move along with the current. These prevent uprooting and breakage of the plant.