In order to produce electricity using tidal power the difference between high and low tides must be at least meters.
a) 2
b) 3
c) 4
d) 5

d) 5 m

Explanation:

Barrages could be built on the ebb side, or flood side, or even both, to produce electricity. Tidal height can vary from location to location over a broad range (4.5-12.4 m). For profitable operations and adequate water head for the turbines, a tidal range of at minimum 7 m is needed.

So, the appropriate option for the given situation is d.

it may be wrong but i think its a