add exerces 2

.gitignore

@@ -4,4 +4,5 @@
 __pycache__
 *.pyc
 *.zip
-*.out
\ No newline at end of file
+*.out
+*.pdf
\ No newline at end of file

data/1.OpenCV初阶/1.OpenCV基础/1.OpenCV简介/helloworld.md

 # Hello World
 
+![](./lena.png)
+
 以下 `Hello World` 程序中，能够正确执行下述操作的是？
 
 1. 读取目录下`lena`图片

data/1.OpenCV初阶/1.OpenCV基础/2.OpenCV安装/config.json

 {
   "keywords": [],
   "children": [],
-  "export": [],
   "node_id": "opencv-662dbd65c89d4ddb9e392f44ffe16e1a",
-  "title": "OpenCV安装"
+  "title": "OpenCV安装",
+  "export": [
+      "install.json"
+  ]
 }
\ No newline at end of file

data/1.OpenCV初阶/1.OpenCV基础/2.OpenCV安装/install.json

+{
+    "type": "code_options",
+    "author": "huanhuilong",
+    "source": "install.md",
+    "notebook_enable": true
+  }
\ No newline at end of file

data/1.OpenCV初阶/1.OpenCV基础/2.OpenCV安装/install.md

+# 极简OpenCV环境安装
+
+OpenCV 的官方教程里提供了各平台的安装教程：https://docs.opencv.org/4.x/df/d65/tutorial_table_of_content_introduction.html
+
+但是最便利的方式是安装 [`opencv-python`](https://codechina.csdn.net/opencv/opencv-python) ，安装命令如下：
+
+```bash
+pip install opencv-python
+```
+
+在 Python 中打印出使用的 OpenCV 版本，<span style="color:red">正确</span>的代码是？。
+
+## template
+
+```python
+import cv2
+print(cv2.__version__)
+```
+
+## 答案
+
+```python
+import cv2
+print(cv2.__version__)
+```
+
+## 选项
+
+### A
+
+```python
+import cv
+print(cv.__version__)
+```
+
+### B
+
+```python
+import opencv
+print(opencv.__version__)
+```
+
+### C
+
+```python
+import opencv_python
+print(opencv_python.__version__)
+```