R语言markdown-html标头问题

---

title: "Task4"

author: "韩冰冰"

date: "2018年8月30日"

output: 

  html_document:

    number_sections: TRUE

    toc: TRUE

    toc_float: TRUE

    code_folding: show

    fig_width: 7

    fig_height: 4.5

    theme: united

    highlight: tango

---



```{r setup, include=FALSE}

knitr::opts_chunk$set(echo = TRUE, message = FALSE, warning = FALSE)

```