$(5$ points$)$ A cold$-$rolled steel sheet from a fully annealed state has a microstructure of severely elongated grains. Compared to the original $($just annealed$)$ material, the rolled material has

a$.$ No changes in mechanical properties

b$.$ A lower yield strength

c$.$ Isotropic mechanical properties

d$.$ Anisotropic mechanical properties

$(2$ points$)$ Strength may NOT be increased by

a$.$ Decreasing grain size

b$.$ Forming solid solutions

c$.$ Hot working strength