Eclipse：Android项目API级别

Question

我在Eclipse中导入了一个Android项目，产生的错误如下：

Multiple markers at this line
- The type java.lang.String cannot be resolved. It is indirectly referenced from required .class files
- The type java.lang.Class cannot be resolved. It is indirectly referenced from required .class files
- The type android.app.Instrumentation cannot be resolved. It is indirectly referenced from required .class 
 files
- The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files

解决方案是安装Android API Level 18.但是，我的问题是 - 在项目中指定了哪个位置？

如果我看project.properties，我会看到：

# This file is automatically generated by Android Tools.
# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
#
# This file must be checked in Version Control Systems.
#
# To customize properties used by the Ant build system edit
# "ant.properties", and override values to adapt the script to your
# project structure.
#
# To enable ProGuard to shrink and obfuscate your code, uncomment this (available properties: sdk.dir, user.home):
#proguard.config=${sdk.dir}/tools/proguard/proguard-android.txt:proguard-project.txt

# Project target.
target=android-18

明确指出API级别18.但是，我不知道它来自何处。例如。查看项目属性我没有看到指定的项目构建目标：

并在Manifest文件中显示<uses-sdk android:minSdkVersion="16" />所以我认为它会使用API Level 17。但事实并非如此。它似乎需要API Level 18。

那么，这是指定的位置？