Jack kept in touch with his friends ((by e-mail)(划线))during his stay in America.(对划线部分提问)_____ _____Jack keep in touch with his friends during his stay in America?

Jack kept in touch with his friends ((by e-mail)(划线))during his stay in America.(对划线部分提问)_____ _____Jack keep in touch with his friends during his stay in America?
Jack kept in touch with his friends ((by e-mail)(划线))during his stay in America.(对划线部分提问)
_____ _____Jack keep in touch with his friends during his stay in America?

Jack kept in touch with his friends ((by e-mail)(划线))during his stay in America.(对划线部分提问)_____ _____Jack keep in touch with his friends during his stay in America?
How did Jack keep in touch with his friends during his stay in America?