On sequential separability of functional spaces

In this paper, we give necessary and sufficient conditions for the space B1(X) of first Baire class functions on a Tychonoff space X, with pointwise topology, to be (strongly) sequentially separable. Also we claim that there are spaces X such that B1(X) is not sequentially separable space, but Cp(X) is sequentially separable (the Sorgenfrey line, the Niemytzki plane).