10 things you need to know before the opening bell

Here is what you need to know.

The IMF warned China. The International Monetary Fund says China must do something about its mounting corporate debt load. Reuters reports, David Lipton, first deputy managing director of the IMF, told a group of economists in Shenzhen, China, "Company debt problems today can become systemic debt problems tomorrow. Systemic debt problems can lead to much lower economic growth, or a banking crisis. Or both." Specifically, Lipton pointed to the debt of state owned enterprises, which total 55% of corporate debt, but account for only 22% of economic output, Reuters says.

China's investment hit a 15-year low. China's fixed asset investment slowed to 9.6% through May, the first time it's been below 10% since 2000. Additionally, retail sales rose 10% year-over-year, just missing the 10.1% that was expected. On Monday, China's yuan fell 0.4% to 6.5864 per dollar, and is nearing its weakest level since the first quarter of 2011.

Betting odds for Britain remaining in the EU are falling. The latest Betfair odds show the likelihood of Britain remaining in the EU are down to 64% from 78% on Thursday. The uncertainty surrounding the vote continues to pressure the British pound, which has fallen more than 3.5% since May 25. Traders will be watching the February low of 1.3871, which, if broken, would produce the lowest print since 1985.

Oil is lower. West Texas Intermediate crude oil trades down about 1% near $48.50 per barrel. Monday's selling extends crude's slide to a third day, during which it has lost about 6%. In a Monday morning email, Mike van Dulken of Accendo Markets wrote, "$50 could be a tough level to surpass for Crude. While Brent is currently in a consolidation pattern (mid-downtrend) around $50, WTI has dropped back below to trade around $48.5."

Bitcoin is surging. The digital currency is higher by almost 20% near $690, and is threatening the $700 level for the first time since February 2014. Monday's gain has bitcoin up almost 30% since the middle of May. The strong gains come as halving, or the reduction of the amount of bitcoins produced by mining, is set to occur later this month.

The final round of bidding for Yahoo's core assets is set. Rivals AT&T and Verizon have made the third and final round of bidding for Yahoo's core assets, Reuters reports. Additionally, a group led Dan Gilbert, the founder of Quicken Loans, and backed by Warren Buffett, also made the next round while a couple of private equity firms did not. Yahoo hopes to complete the process by next month, a person familiar with the matter told Reuters.

Walgreens has terminated its relationship with Theranos. A statement posted on Walgreens' website says it is shutting down all 40 Theranos' wellness centers at Walgreens stores in Arizona. The decision by Walgreens is a huge blow to Theranos as the wellness centers were the company's primary source of revenue, according to the Wall Street Journal. "Quality and safety are our top priorities and we are working closely with government officials to ensure that we not only comply with all federal regulations but exceed them," Theranos spokesperson Brooke Buchanan told Business Insider.

Apple's Worldwide Developers Conference is happening. The WWDC kicks off in San Francisco. According to The Verge, Siri will be the main focus of the event. Other areas of focus for the event include Apple Music, Apple Pay, and iOS.

Stocks everywhere are under pressure. Japan's Nikkei (-3.5%) was hit hard overnight, and Spain's IBEX (-1.6%) leads the losses in Europe. S&P 500 futures are down 8.75 points at 2087.50.

US economic data is absent. Data picks up on Tuesday with import/export prices, retail sales, and business inventories. The US 10-year yield is down two basis points at 1.62%.