Fix grammatical error

foundations/javascript_basics/object_basics.md

@@ -83,7 +83,7 @@ increaseCounterPrimitive(primitive);
 
 Take a moment and guess what will happen to `object` and what will happen to `primitive` after we make the function calls.
 
-If you answered that the object counter would increase by 1, and the primitive counter wouldn't change, you're correct. Remember that the parameter `objectCounter` contains a *reference* to the same object as the `object` variable we gave it, while `primitiveCounter` contains only a copy of the primitive value only.
+If you answered that the object counter would increase by 1, and the primitive counter wouldn't change, you're correct. Remember that the parameter `objectCounter` contains a *reference* to the same object as the `object` variable we gave it, while `primitiveCounter` only contains a copy of the primitive value.
 
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