<select name="options[foo]">
<option value="1" <?php if ( $options['foo'] == 1 ) echo 'selected="selected"'; ?>>1</option>
<option value="2" <?php if ( $options['foo'] == 2 ) echo 'selected="selected"'; ?>>2</option>
<option value="3" <?php if ( $options['foo'] == 3 ) echo 'selected="selected"'; ?>>3</option>
</select>
<select name="options[foo]">
<option value="1" <?php selected( $options['foo'], 1 ); ?>>1</option>
<option value="2" <?php selected( $options['foo'], 2 ); ?>>2</option>
<option value="3" <?php selected( $options['foo'], 3 ); ?>>3</option>
</select>