Merge pull request apollographql#3779 from apollographql/hwillson/def…

…ault-options-docs

Doc change for `defaultOptions.watchQuery` when using React Apollo [apollographql#3779]

docs/source/api/apollo-client.md

@@ -34,6 +34,8 @@ const defaultOptions = {
 
 These options will be merged with options supplied with each request.
 
+> **Note:** The React Apollo `<Query />` component uses Apollo Client's `watchQuery` functionality, so if you would like to set `defaultOptions` when using `<Query />`, be sure to set them under the `defaultOptions.watchQuery` property.
+
 The `ApolloClient` class is the core API for Apollo, and the one you'll need to  use no matter which integration you are using:
 
 {% tsapibox ApolloClient.constructor %}