How to display the chosen item_option of a product as selected option in the cart? - CartThrob

Question

I am using the update_cart_form nested inside the cart_items_info tag, to allow customers to edit the size or quantity of their item (as well as delete it from cart). I cannot find a way to have the item option they selected as the selected option in the (for example, if Medium is selected under the product_size, display that as the selected option)

I would also like to replicate this for displaying their currently chosen shipping method. Here is the code I currently am using:

{exp:cartthrob:cart_items_info}
    {if no_results}
        <p>You have nothing in your cart. <a class="blue" href="/shop">GO SHOP &raquo;</a></p>
    {/if}
    {if total_items > 0}
        {if first_row}
             {exp:cartthrob:update_cart_form  return="checkout" class="cart_form"}
        {/if}
                <ul class="cart-table">
                    {if product_detail_image}
                        <img src="{product_detail_image:feed}"/>
                    {if:else}
                        <img src="{site_url}content/img/ride.png"/>
                    {/if}
                    <li><p>{title} <span>Quantity: <input type="text" name="quantity[{row_id}]" size="1" maxlength="2" value="{quantity}" /></span></p>
                        <p>{exp:cartthrob:item_options entry_id="{entry_id}" }
                        {if dynamic}
                            <label>{option_label}</label>
                            {input}
                        {if:else}
                            {if options_exist}
                                {select}  
                                    <option {selected} value="{option_value}">
                                    {option_name}{if option_price_numeric > 0} +{option_price}{/if}
                                    </option>
                                {/select}
                            {/if}
                        {/if}
                        {/exp:cartthrob:item_options}
                        <span><input type="checkbox" name="delete[{row_id}]"> Delete this item</span></p>
                    </li>
                </ul>
            {if last_row}
                <select name="shipping_option">
                        {exp:cartthrob:get_shipping_options}
                                <option value="{rate_short_name}" {selected}>{rate_title} - {rate_price}</option>
                        {/exp:cartthrob:get_shipping_options}
                </select>
                <input type="submit" value="Update Cart" />
            {/exp:cartthrob:update_cart_form}
        {/if}
    {/if}
{/exp:cartthrob:cart_items_info}

Answer 1

Instead of using:

<option {selected} value="{option_value}">

Use:

<option {if selected}selected{/if} value="{option_value}">

Also, add the row_id parameter to your {exp:cartthrob:item_options} tag.
ie.

{exp:cartthrob:item_options row_id="{row_id}"}