Alphabet Class C shares slid 0.5% to $321.52 in early Monday trading, following a report that the Google parent is lining up an investment-grade bond sale of around $15 billion to support its expansion plans. The issue could be sliced into as many as seven tranches, with the longest rumored to mature in 2066, priced at about 1.2 percentage points above Treasuries, the report said. Alphabet has yet to comment; a regulatory filing didn’t specify the exact size.