The correct answer is (A).
The artist had to struggle a lot before being recognized for his talent. This means that he had to work hard and overcome many challenges in order to achieve success.
The other options are not as accurate.
(B) Toil means to work hard and long, but it does not necessarily mean that the artist had to struggle.
(C) Practice means to do something repeatedly in order to improve, but it does not necessarily mean that the artist had to struggle.
(D) Effort means to use energy and concentration in order to do something, but it does not necessarily mean that the artist had to struggle.
(E) Strive means to try hard to achieve something, but it does not necessarily mean that the artist had to struggle.