The statement that is true regarding store credit cards is:
They usually have interest rates of 5 to 10 percentage points higher than those of ordinary credit cards.
Store credit cards typically have higher interest rates compared to general credit cards. The other options are generally not true: store credit cards are usually not co-branded with Visa, MasterCard, or American Express, they are typically limited to use at specific stores, and while the grace period may vary, it's not universally set at 28 days.