Following is code....
1.Drawing a line with multiple values.
<telerik:RadHtmlChart runat="server" ID="chart1" Width="800" Height="500" Transitions="true">
<PlotArea>
<Series>
<telerik:LineSeries Name="Line Series">
<LineAppearance LineStyle="Step" />
<Appearance>
<FillStyle BackgroundColor="Green" />
</Appearance>
<LabelsAppearance Visible="false" />
<MarkersAppearance Visible="false" />
<SeriesItems>
<telerik:CategorySeriesItem Y="200" />
<telerik:CategorySeriesItem Y="200" />
<telerik:CategorySeriesItem Y="200" />
<telerik:CategorySeriesItem Y="200" />
<telerik:CategorySeriesItem Y="200" />
<telerik:CategorySeriesItem Y="200" />
<telerik:CategorySeriesItem Y="200" />
</SeriesItems>
</telerik:LineSeries>
</Series>
<CommonTooltipsAppearance Color="White"></CommonTooltipsAppearance>
<XAxis>
<MajorGridLines Color="#EFEFEF" Width="1" />
<MinorGridLines Color="#F7F7F7" Width="1" />
<Items>
<telerik:AxisItem LabelText="2008" />
<telerik:AxisItem LabelText="2009" />
<telerik:AxisItem LabelText="2010" />
<telerik:AxisItem LabelText="2011" />
<telerik:AxisItem LabelText="2012" />
<telerik:AxisItem LabelText="2013" />
<telerik:AxisItem LabelText="2014" />
</Items>
<TitleAppearance Position="Center" Text="Years" />
</XAxis>
<YAxis>
<MajorGridLines Color="#EFEFEF" Width="1" />
<MinorGridLines Color="#F7F7F7" Width="1" />
<TitleAppearance Position="Center" Text="Finance" />
</YAxis>
</PlotArea>
<ChartTitle Text="Company Performance">
<Appearance Align="Center" Position="Top" />
</ChartTitle>
<Legend>
<Appearance Position="Bottom" />
</Legend>
</telerik:RadHtmlChart>
2.Not drawing a line with single value.
<telerik:RadHtmlChart runat="server" ID="chart1" Width="800" Height="500" Transitions="true">
<PlotArea>
<Series>
<telerik:LineSeries Name="Line Series">
<LineAppearance LineStyle="Step" />
<Appearance>
<FillStyle BackgroundColor="Green" />
</Appearance>
<LabelsAppearance Visible="false" />
<MarkersAppearance Visible="false" />
<SeriesItems>
<telerik:CategorySeriesItem Y="200" />
</SeriesItems>
</telerik:LineSeries>
</Series>
<CommonTooltipsAppearance Color="White"></CommonTooltipsAppearance>
<XAxis>
<MajorGridLines Color="#EFEFEF" Width="1" />
<MinorGridLines Color="#F7F7F7" Width="1" />
<Items>
<telerik:AxisItem LabelText="2008" />
<telerik:AxisItem LabelText="2009" />
<telerik:AxisItem LabelText="2010" />
<telerik:AxisItem LabelText="2011" />
<telerik:AxisItem LabelText="2012" />
<telerik:AxisItem LabelText="2013" />
<telerik:AxisItem LabelText="2014" />
</Items>
<TitleAppearance Position="Center" Text="Years" />
</XAxis>
<YAxis>
<MajorGridLines Color="#EFEFEF" Width="1" />
<MinorGridLines Color="#F7F7F7" Width="1" />
<TitleAppearance Position="Center" Text="Finance" />
</YAxis>
</PlotArea>
<ChartTitle Text="Company Performance">
<Appearance Align="Center" Position="Top" />
</ChartTitle>
<Legend>
<Appearance Position="Bottom" />
</Legend>
</telerik:RadHtmlChart>
Please find the attached files.