All banks, trust companies, savings associations, investment companies, and other persons carrying on an investment business, all insurance companies, insurance associations, and other persons carrying on an insurance business, and all executors, administrators, guardians, trustees, and other fiduciaries may legally invest any sinking funds, moneys, or other funds belonging to them or within their control in any bonds or notes issued pursuant to this subchapter; provided, however, that nothing contained in this section may be construed as relieving any persons from any duty of exercising reasonable care in selecting securities for purchase or investment.