http://mywebsite-dev/blog/_api/web/lists/getByTitle('Posts')/items?$select=Title,Body,Id,LikesCount,NumCommentsId

{
    "d": {
        "results": [
            {
                "__metadata": {
                    "id": "Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(2)",
                    "uri": "http://mywebsite-dev/blog/_api/Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(2)",
                    "etag": ""1"",
                    "type": "SP.Data.PostsListItem"
                },
                "Id": 2,
                "Title": "Blog 1",
                "Body": "<div class="ExternalClass30B2DE63AD2D4EE1AC4DD2735266245C"><p>This is my blog 1•</p></div>",
                "NumCommentsId": 0,
                "LikesCount": null,
                "ID": 2
            },
            {
                "__metadata": {
                    "id": "Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(3)",
                    "uri": "http://mywebsite-dev/blog/_api/Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(3)",
                    "etag": ""1"",
                    "type": "SP.Data.PostsListItem"
                },
                "Id": 3,
                "Title": "Blog 2",
                "Body": "<div class="ExternalClass9FDE8E9403FF43F3BEE2BC24798EDA16"><p>This is second cloud blog•</p></div>",
                "NumCommentsId": 3,
                "LikesCount": null,
                "ID": 3
            }
        ]
    }
}

{
    "d": {
        "results": [
            {
                "__metadata": {
                    "id": "Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(2)",
                    "uri": "http://mywebsite-dev/blog/_api/Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(2)",
                    "etag": ""1"",
                    "type": "SP.Data.PostsListItem"
                },
                "Id": 2,
                "Title": "Blog 1",
                "Body": "<div class="ExternalClass30B2DE63AD2D4EE1AC4DD2735266245C"><p>This is my blog 1•</p></div>",
                "NumCommentsId": 0,
        "Comments":{}
                "LikesCount": null,
                "ID": 2
            },
            {
                "__metadata": {
                    "id": "Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(3)",
                    "uri": "http://mywebsite-dev/blog/_api/Web/Lists(guid'862870c0-e56b-48ca-9da4-b337d05984aa')/Items(3)",
                    "etag": ""1"",
                    "type": "SP.Data.PostsListItem"
                },
                "Id": 3,
                "Title": "Blog 2",
                "Body": "<div class="ExternalClass9FDE8E9403FF43F3BEE2BC24798EDA16"><p>This is second cloud blog•</p></div>",
                "NumCommentsId": 3,
        "Comments":[
                {
                "Id":1,
                "Title":"My Comment Title",
                "Body":"My Comment Body"
                },
                {
                "Id":2,
                "Title":"My second Comment Title",
                "Body":"My second Comment Body"
                },

                {
                "Id":3,
                "Title":"My third Comment Title",
                "Body":"My third Comment Body"
                },
               ]
                "LikesCount": null,
                "ID": 3
            }
        ]
    }
}

$select=Title,Body,Id,LikesCount,NumCommentsId,Comments&$expand=Comments