Wbjee answer key has been removed from the official website so it is difficult to get it but i am sharing you a link from which you can see the answer key given by the coaching institutes for wbjee 2019. Answer key by coaching institute are also correct.

Link:

https://www.google.co.in/url?sa=i&source=web&cd=&ved=2ahUKEwidrva3ivbiAhVVdCsKHdMtBtwQzPwBegQIARAC&url=https%3A%2F%2Fengineering.careers360.com%2Farticles%2Fwbjee-answer-key&psig=AOvVaw3pHgSpwZeBmvcUAYYuNdjV&ust=1561052115707133

I am also giving you another link from this you can also see the video solutions 

Link:

https://www.google.co.in/url?sa=i&source=web&cd=&ved=2ahUKEwig6JzBi_biAhUMfH0KHSkLDVcQzPwBegQIARAC&url=https%3A%2F%2Fadmission.aglasem.com%2Fwbjee-answer-key-mathematics%2F&psig=AOvVaw0Ck9XeGKwSUJm_VK0I0nc0&ust=1561052403647832