Пре­об­ра­зуй­те, если это не­об­хо­ди­мо, слово EFFECTIVE так, чтобы оно грам­ма­ти­че­ски и лек­си­че­ски со­от­вет­ство­ва­ло со­дер­жа­нию тек­ста.

Morse used a dots-⁠and-⁠spaces code for the letters of the alphabet and for numbers. It was later improved to use dashes with dots and spaces. Since then, it has proved its ___________ many times.